A thin prism p1 with angle 4° and made from glass of refractive index 1.54 is combined with another thin prism p2 made from glass of refractive index 1.72 to produce dispersion without deviation. The angle of prism p2 is
In the formation of a rainbow light from the sun on water droplets undergoes
Find the co-ordinates of image of the point object ‘O’ formed after reflection from concave mirror as shown figure assuming prism to be thin and small in size and of prism angle 2 ∘ . Refractive index of the prism material is 3 2 . Do not consider the refraction of the rays from the prism after reflection from concave mirror.
A convex lens, a glass slab, a glass prism and a solid sphere all are made of the same glass, the dispersive power will be
A point object is placed at a distance of 25 cm from a convex lens. Its focal length is 22 cm. A glass slab to refractive index 1.5 is inserted between the lens and the object, then the image is formed at infinity. Find the thickness of the glass slab (in cm).
The radius of concave surface is 20 cm and radius of convex surface is 10 cm. The refractive index of material of lens is 1.5. If image of point object P coincides with it. Find the distance (in cm) between object and lens.
Diameter of a plano-convex lens is 6 cm and thickness at the center is 3 mm. If the speed of light in material of lens is 2 × 10 8 m s − 1 . The focal length of the lens is in ……..cm.
An object is placed at 20cm from a convex mirror of focal length 10cm. The image formed by the mirror is
Under which of the following conditions will a convex mirror of focal length f produce an image that is erect, diminished and virtual
A concave mirror of focal length 15 cm forms an image having twice the linear dimensions of the object. The position of the object when the image is virtual will be
The ratio of the refractive index of red light to blue light in air is
How much water ( level from bottom in cm )should be filled in a container 21 cm in height, so that it appears half filled when viewed from the top of the container (given that a μ ω = 4 3 )
A light wave has a frequency of 4 × 10 14 Hz and a wavelength of 5 × 10 − 7 meters in a medium. The refractive index of the medium is
‘Mirage’ is a phenomenon due to
A fist looking from within water sees the outside world through a circular horizon. If the fish 7 cm below the surface of water, what will be the radius of the circular horizon
A converging lens is used to form an image on a screen. When upper half of the lens is covered by an opaque screen
A thin convex lens of refractive index 1.5 has a focal length of 15 cm in air. When the lens is placed in liquid of refractive index 4 3 , its focal length will be
If I 1 and I 2 be the size of the images respectively for the two positions of lens in the displacement method, then the size of the object is given by
A circular disc of which 2 3 part is coated with yellow and 1 3 part is with blue. It is rotated about its central axis with high velocity, then it will be seen as
The minimum deviation produced by a hollow prism filled with a certain liquid is found to be 30°. The light ray is also found to be refracted at angle of 30°. The refractive index of the liquid is
An achromatic prism is made by combining two prisms P 1 μ v = 1 .523 , μ r = 1 .515 and P 2 μ v = 1 .666 , μ r = 1 .650 where μ represents the refractive index. If the angle of the prism P1 is 10°, then the angle of the prism P2 will be
When seen in green light, the saffron and green portions of our National Flag will appear to be
Colour of the sky is blue due to
A prism of refracting angle 60° is made with a material of refractive index μ . For a certain wavelength of light, the angle of minimum deviation is 30°. For this, wavelength the value of refractive index of the material is
If the angle of prism is 60° and the angle of minimum deviation is 40°, the angle of refraction will be
A ray incident a 15° on one refracting surface of a prism of angle 60°, suffers a deviation of 55°. What is the angle of emergence
The impact of an image on the retina remains for
When objects at different distances are seen by the eye, which of the following remains constant
The light when enters the human eye experiences most of the refraction while passing through
A man with defective eyes cannot see distinctly object at the distance more than 60 cm from his eyes. The power of the lens to be used will be
The radius of curvature of the convex face of a planoconvex lens is 12 cm and its refractive index is 1.5. What is the focal length of the lens?
The figure shows a light ray starting from the corner E of the bottom of a tank filled with a liquid reaching an observer O. The refractive index of the liquid with respect to air is
One face of a rectangular glass plate, 6 cm thick, is silvered. An object held 8 cm in front of the first face forms an image 12 cm behind the silvered face. The refractive index of the glass is
A mirror is inclined at an angle of with the horizontal. If a ray of light is incident at an angle as shown, then the angle made by reflected ray with the horizontal is
What should be refractive index of a transparent medium to be invisible in vacuum?
A prism of angle A = 1º has a refractive index μ = 1.5 . A good estimate for the minimum angle of deviation (in degrees) is close to N/10. Value of N is
The refractive index of material of prism is given by μ = sin A + D m 2 sin A 2 , A & D m have their usual meanings. A glass prism of A = 60 0 gives minimum angle of deviation at 30 0 with maximum error of 1 0 , when a beam of parallel light passed through prism during experiment. Then percentage error in the measurement of μ of material of prism is
A ray of light incidents on a plane mirror at an angle of 30°. The deviation produced in the ray is
A ray of light is incidenting normally on a plane mirror. The angle of reflection will be
A plane mirror makes an angle of 30° with horizontal. If a vertical ray strikes the mirror, find the angle between mirror and reflected ray
When a plane mirror is rotated through an angle θ then the reflected ray turns through the angle 2 θ then the size of the image
A man runs towards mirror at a speed of 15 m/s. What is the speed of his image?
A man runs towards a mirror at a speed 15 m/s. The speed of the image relative to the man is
A man of length h requires a mirror, to see his own complete image of length at least equal to
A boy stands straight infront of a mirror at a distance of 30cm away from it. He sees his erect image whose height is 1 5 th of his real height. The mirror he is using is
If an object is placed 10cm infront of a concave mirror of focal length 20cm, the image will be
A concave mirror is used to focus the image of a flower on a nearby well 120 cm from the flower. If a lateral magnification of 16 is desired, the distance of the flower from the mirror should be
If an object is placed 10cm infront of a concave mirror of focal length 20cm, the image will be
An object is placed 40cm from a concave mirror of focal length 20 cm. The image formed is
A concave mirror gives an image three times as large as the object placed at a distance of 20cm from it. For the image to be real, the focal length should be
What will be the height of image when an object of 2 mm is placed on the axis of a convex mirror at a distance 20 cm of radius of curvature 40 cm
The refractive index of a piece of transparent quartz is the greatest for
The index of refraction of diamond is 2.0, velocity of light in diamond in cm/second is approximately
A monochromatic beam of light passes from a denser medium into a rarer medium. As a result
A cut diamond sparkles because of its
A fish is a little away below the surface of a lake. If the critical angle is 49°, then the fish could see things above the water surface within an angular range of θ ∘ where
The phenomenon utilised in an optical fibre is
Consider telecommunication through optical fibres. Which of the following statements is not true?
Light wave enters from medium 1 to medium 2. Its velocity in 2nd medium is double from 1st. For total internal reflection the angle of incidence must be greater than
Glass has refractive index μ with respect to air and the critical angle for a ray of light going from glass to air is θ . If a ray of light is incident from air on the glass with angle of incidence θ , the corresponding angle of refraction is
In the figure shown, for an angle of incidence 45° at the top surface, what is the minimum refractive index needed for total internal reflection at vertical face
The critical angle of a medium with respect to air is 45° . The refractive index of medium is
If light travels a distance x in t 1 sec in air and 10 x distance in t 2 sec in a medium, the critical angle of the medium will be
A concave and convex lens have the same focal length of 20 cm and are put into contact to form a lens combination. The combination is used to view an object of 5 cm length kept at 20 cm from the lens combination. As compared to the object, the image will be
A glass lens is placed in a medium in which it is found to behave like a glass plate. Refractive index of the medium will be
A double convex lens of focal length 20 cm is made of glass of refractive index 3 2 . When placed completely in water a μ w = 4 3 , its focal length will be
An object is placed at a distance of f 2 from a convex lens. The image will be
A plano convex lens (f = 20 cm) is silvered at plane surface. Now f will be
A thin double convex lens has radii of curvature each of magnitude 40 cm and is made of glass with refractive index 1.65. Its focal length is nearly
The focal length of lens of refractive index 1.5 in air is 30 cm. When it is immersed in a liquid of refractive index 4 3 , then its focal length in liquid will be
A magnifying glass is to be used at the fixed object distance of 1 inch. If it is to produce an erect image magnified 5 times its focal length should be
In a parallel beam of white light is incident on a converging lens, the colour which is brought to focus nearest to the lens is
A film projector magnifies a 100 cm 2 film strip on a screen. If the linear magnification is 4, the area of magnified film on the screen is
At what distance from a convex lens of focal length 30 cm, an object should be placed so that the size of the image be 1/2 of the object
The radius of the convex surface of plano-convex lens is 20 cm and the refractive index of the material of the lens is 1.5. The focal length of the lens is
A thin plano-convex lens acts like a concave mirror of focal length 0.2 m when silvered from its plane surface. The refractive index of the material of the lens is 1.5. The radius of curvature of the convex surface of the lens will be
The focal lengths of convex lens for red and blue light are 100 cm and 96.8 cm respectively. The dispersive power of material of lens is
A convex lens is in contact with concave lens. The magnitude of the ratio of their focal length is 2 3 . Their equivalent focal length is 30 cm. What are their individual focal lengths
A combination of two thin convex lenses of focal length 0.3 m and 0.1 m will have minimum spherical and chromatic aberrations if the distance between them is
The focal length of the field lens (which is an achromatic combination of two lenses) of telescope is 90 cm. The dispersive powers of the two lenses in the combination are 0.024 and 0.036. The focal lengths of two lenses are
The dispersion for a medium of wavelength λ is D, then the dispersion for the wavelength 2 λ will be
A parallel beam of monochromatic light is incident at one surface of a equilateral prism. Angle of incidence is 55° and angle of emergence is 46°. The angle of minimum deviation will be
Light rays from a source are incident on a glass prism of index of refraction μ and angle of prism α . At near normal incidence, the angle of deviation of the emerging rays is
By placing the prism in minimum deviation position, images of the spectrum
Dispersion can take place for
A triangular prism of glass is shown in the figure. A ray incident normally to one face is totally reflected, if θ = 45 ∘ . The index of refraction of glass is
Which of the following diagrams, shows correctly the dispersion of white light by a prism
A white screen illuminated by green and red light appears to be
Which one of the following alternative is FALSE for a prism placed in a position of minimum deviation
Lens used to remove long sightedness (hypermetropia) is or A person suffering from hypermetropia requires which type of spectacle lenses
Substance on the choroid is
Circular part in the centre of retina is called
Image is formed for the short sighted person at
A man cannot see clearly the objects beyond a distance of 20 cm from his eyes. To see distant objects clearly he must use which kind of lenses and of what focal length
The hyper-metropia is a
The angular dispersion produced by a prism
Light enters at an angle of incidence in a transparent rod of refractive index n. For what value of the refractive index of the material of the rod the light once entered into it will not leave it through its lateral face what so ever be the value of angle of incidence?
A beam of monochromatic light is refracted from vacuum into a medium of refractive index 1.5, the wavelength of refracted light will be
An astronomical telescope has a large aperture to
An equilateral prism is placed on a horizontal surface. A ray PQ is incident onto it. For minimum deviation
Two convex lenses placed in contact form the image of a distant object at P. If the lens B is moved to the right, the image will
Find the number of images of point source S formed by combination of three plane mirrors as shown in the figure.
A point object in air is in front of the curved surface of a plano-convex lens. The radius of curvature of the curved surface is 30cm and the refractive index of the lens material is 1.5, then the focal length of the lens (in cm) is
There is a small source of light at some depth below the surface water (refractive index = 4 3 ) in a tank of large cross sectional surface area. Neglecting any reflection from the bottom and absorption by water, percentage of light that emerges out of surface is (nearly): [use the fact that surface area of a spherical cap of height and radius of curvature r is 2 π r h ]
A ray incident on a droplet of water at an angle of incidence i undergoes two reflections (not total) and emerges. If the deviation suffered by the ray within the drop is minimum and the refractive index of the droplet be μ , then cos i = μ 2 – 1 x . Find the value of x .
A ray is incident normally on a right angle prism whose refractive index is 3 and prism angle α = 30 ° , after crossing prism ray passes through glass sphere. It strikes the glass sphere of same refractive index, at R 2 distance from principal axis, as shown in the figure, sphere is half polished. The net angle of deviation of the incident ray is
An astronomical telescope having focal length of objective 300 cm and of eyepiece 5 cm. It is focused to see an object 20 km from the objective. If final image is formed at infinity, then:
A fish rising up vertically toward the surface of water with speed 3 ms -1 observes a bird diving down vertically towards it with speed 9 ms -1 . The actual velocity of bird is
A light bulb is placed between two plane mirrors inclined at an angle of 60°. The number of images formed are
It is desired to photograph the image of an object placed at a distance of 3m from the plane mirror. The camera which is at a distance of 4.5m from the mirror should be focussed for a distance of
A thick plane mirror shows a number of images of the filament of an electric bulb. Of these, the brightest image is the
When a plane mirror is placed horizontally on a level ground at a distance of 60m from the foot of a tower, the top of the tower and its image in the mirror subtend an angle of 90° at the eye. The height of the tower will be
When light wave suffers reflection at the interface from air to glass, the change in phase of the reflected wave is equal to
The light reflected by a plane mirror may form a real image
An object is at a distance of 0.5 m in front of a plane mirror. Distance between the object and image is
A convex mirror is used to form the image of an object. Then which of the following statements is wrong
Given a point source of light, which of the following can produce a parallel beam of light
A virtual image larger than the object can be obtained by
Match List I with List II and select the correct answer using the codes given below the lists : List I (Position of the object) List II (Magnification) (I) An object is placed at focus before a convex mirror (A) Magnification is – ∞ (II) An object is placed at centre of curvature before a concave mirror (B) Magnification is 0.5 (III) An object is placed at focus before a concave mirror (C) Magnification is +1 (IV) An object is placed at centre of curvature before a convex mirror (D) Magnification is – 1 (E) Magnification is 0.33
Which of the following form(s) a virtual and erect image for all positions of the object
A concave mirror of focal length f (in air) is immersed in water ( μ = 4 3 ). The focal length of the mirror in water will be
To an observer on the earth the stars appear to twinkle. This can be ascribed to
The refractive index of a certain glass is 1.5 for light whose wavelength in vacuum is 6000 Å . The wavelength of this light when it passes through glass is
When light travels from one medium to the other of which the refractive index is different, then which of the following will change
A diver in a swimming pool wants to signal his distress to a person lying on the edge of the pool by flashing his water proof flash light
Critical angle is that angle of incidence in the denser medium for which the angle of refraction in rarer medium is
With respect to air critical angle in a medium for light of red colour [ λ 1 ] is θ . Other facts remaining same, critical angle for light of yellow colour [ λ 2 ] will be
The reason for shining of air bubble in water is
A ray of light travelling in a transparent medium falls on a surface separating the medium from air at an angle of incidence of 45°. The ray undergoes total internal reflection. If n is the refractive index of the medium with respect to air, select the possible value (s) of n from the following
When a ray of light emerges from a block of glass, the critical angle is
Total internal reflection is possible when light rays travel
A ray of light propagates from glass (refractive index = 3 2 ) to water (refractive index = 4 3 ). The value of the critical angle
The refractive index of water is 1.33. The direction in which a man under water should look to see the setting sun is
Optical fibres are related with
If critical angle for a material to air is 30°, the refractive index of the material will be
A light ray from air is incident (as shown in figure) at one end of a glass fiber (refractive index μ = 1.5) making an incidence angle of 60° on the lateral surface, so that it undergoes a total internal reflection. How much time would it take to traverse the straight fiber of length 1 km
The critical angle for a medium is 60°. The refractive index of the medium is
A normally incident ray reflected at an angle of 90°. The value of critical angle is
The phenomena of total internal reflection is seen when angle of incidence is
The radius of curvature for a convex lens is 40 cm, for each surface. Its refractive index is 1.5. The focal length will be
A thin lens focal length f 1 and its aperture has diameter d. It forms an image of intensity I. Now the central part of the aperture upto diameter d 2 is blocked by an opaque paper. The focal length and image intensity will change to
A lens of power + 2 diopters is placed in contact with a lens of power – 1 diopter. The combination will behave like
Two similar plano-convex lenses are combined together in three different ways as shown in the adjoining figure. The ratio of the focal lengths in three cases will be
A thin convex lens of focal length 10 cm is placed in contact with a concave lens of same material and of same focal length. The focal length of combination will be
Focal length of a convex lens will be maximum for
A lens behaves as a converging lens in air and a diverging lens in water. The refractive index of the material is
If the central portion of a convex lens is wrapped in black paper as shown in the figure
A convex lens of focal length 12 cm is made of glass of μ = 3 2 . What will be its focal length when immersed in liquid of μ = 5 4
Two lenses have focal lengths f 1 and f 2 and their dispersive powers are ω 1 and ω 2 respectively. They will together form an achromatic combination if
An equiconvex lens of glass of focal length 0.1 metre is cut along a plane perpendicular to principle axis into two equal parts. The ratio of focal length of new lenses formed is
A lens of refractive index n is put in a liquid of refractive index n ` of focal length of lens in air is f, its focal length in liquid will be
An achromatic combination of lenses produces
A plano-convex lens is made of refractive index of 1.6. The radius of curvature of the curved surface is 60 cm. The focal length of the lens is
A plano-convex lens of refractive index 1.5 and radius of curvature 30 cm is silvered at the curved surface. Now this lens has been used to form the image of an object. At what distance from this lens an object be placed in order to have a real image of the size of the object
The power of an achromatic convergent lens of two lenses is + 2D. The power of convex lens is + 5D. The ratio of dispersive power of convex and concave lens will be
Two lenses of power + 12 and – 2 diopters are placed in contact. The combined focal length of the combination will be
When light rays from the sun fall on a convex lens along a direction parallel to its axis
A thin glass (refractive index 1.5) lens has optical power of -5D in air. It’s optical power in a liquid medium with refractive index 1.6 will be
A concave lens and a convex lens have same focal length of 20 cm and both put in contact this combination is used to view an object 5 cm long kept at 20 cm from the lens combination. As compared to object the image will be
A prism ( μ = 1 .5 ) has the refracting angle of 30°. The deviation of a monochromatic ray incident normally on its one surface will be (sin 48° 36’ = 0.75)
Light from sodium lamp is passed through cold sodium vapours, the spectrum of transmitted light consists of
Our eye is most sensitive for which of the following wavelength
Which of the following element was discovered by study of Fraunhofer lines?
The refractive indices of violet and red light are 1.54 and 1.52 respectively. If the angle of prism is 10°, then the angular dispersion is
If the refractive indices of a prism for red, yellow and violet colours be 1.61, 1.63 and 1.65 respectively, then the dispersive power of the prism will be
Minimum deviation is observed with a prism having angle of prism A, angle of deviation δ , angle of incidence i and angle of emergence e. We then have generally
Angle of a prism is 30° and its refractive index is 2 and one of the surface is silvered. At what angle of incidence, a ray should be incident on one surface so that after reflection from the silvered surface, it retraces its path.
The figures represent three cases of a ray passing through a prism of angle A. The case corresponding to minimum deviation is
When light emitted by a white hot solid is passed through a sodium flame, the spectrum of the emergent light will show
A ray of light incident normally on an isosceles right angled prism travels as shown in the figure. The least value of the refractive index of the prism must be
A source emits light of wavelength 4700Å, 5400 Å and 6500 Å. The light passes through red glass before being tested by a spectrometer. Which wavelength is seen in the spectrum
A ray passes through a prism of angle 60° in minimum deviation position and suffers a deviation of 30°. What is the angle of incidence on the prism?
A thin prism P1 with angle 6° and made from glass of refractive index 1.54 is combined with another thin prism p 2 of refractive index 1.72 to produce dispersion without deviation. The angle of prism P 2 will be
The splitting of white light into several colours on passing through a glass prism is due to
The path of a refracted ray of light in a prism is parallel to the base of the prism only when the
The refractive index of the material of the prism for violet colour is 1.69 and that for red is 1.65. If the refractive index for mean colour is 1.66, the dispersive power of the material of the prism
The deviation caused in red, yellow and violet colours for crown glass prism are 2.84°, 3.28° and 3.72° respectively. The dispersive power of prism material is
When a glass prism of refracting angle 60° is immersed in a liquid its angle of minimum deviation is 30°. The critical angle of glass with respect to the liquid medium is
Why sun has elliptical shape on the time when rising and sun setting ? It is due to
A prism of refractive index μ and angle A is placed in the minimum deviation position. If the angle of minimum deviation is A, then the value of A in terms of μ is
The refractive index of the material of the prism for violet colour is 1.69 and that for red is 1.65. If the refractive index for mean colour is 1.66, the dispersive power of the material of the prism
White light is passed through a prism ……….. colour shows minimum deviation
Sir C.V. Raman was awarded Nobel Prize for his work connected with which of the following phenomenon of radiation
The sky would appear red instead of blue if
A far sighted man who has lost his spectacles, reads a book by looking through a small hole (3-4 mm) in a sheet of paper. The reason will be
A man can see the object between 15 cm and 30 cm. He uses the lens to see the far objects. Then due to the lens used, the near point will be at
An imaginary line joining the optical centre of the eye lens and the yellow point is called as
A person can see clearly only upto a distance of 25 cm. He wants to read a book placed at a distance of 50 cm. What kind of lens does he require for his spectacles and what must be its power
A person is suffering from myopic defect. He is able to see clear objects placed at 15 cm. What type and of what focal length of lens he should use to see clearly the object placed 60 cm away?
In human eye the focussing is done by
The human eye has a lens which has a
A person is suffering from the defect astigmatism. Its main reason is
Myopia is due to
A person who can see things most clearly at a distance of 10 cm. Requires spectacles to enable to him to see clearly things at a distance of 30 cm. What should be the focal length of the spectacles
Far points of myopic eye is 250 cm, then the focal length of the lens to be used will be
Image formed on retina of eye is proportional to
A defective eye cannot see close objects clearly because their image is formed
Ability of the eye to see objects at all distances is called
Identify the wrong description of the above figures
Microscope is an optical instrument which
A person using a lens as a simple microscope sees an
Finger prints are observed by the use of
The exposure time of a camera lens at the f 2 .8 setting is 1 200 second. The correct time of exposure at f 5 .6 is
The magnifying power of a microscope with an objective of 5 mm focal length is 400. The length of its tube is 20 cm. Then the focal length of the eye-piece is
To produce magnified erect image of a far object, we will be required along with a convex lens, is
The objective of a compound microscope is essentially
An electron microscope is superior to an optical microscope in
The magnifying power of a compound microscope increases when
The separation between two microscopic particles is measured P A and P B by two different lights of wavelength 2000 Å and 3000 Å respectively, then
In a compound microscope, the intermediate image is
Two points separated by a distance of 0.1 mm can just be resolved in a microscope when a light of wavelength 6000 Å is used. If the light of wavelength 4800Å is used this limit of resolution becomes
A simple telescope, consisting of an objective of focal length 60 cm and a single eye lens of focal length 5 cm is focussed on a distant object is such a way that parallel rays comes out from the eye lens. If the object subtends an angle 2° at the objective, the angular width of the image
The focal length of objective and eye lens of a astronomical telescope are respectively 2 m and 5 cm. Final image is formed at (i) least distance of distinct vision (ii) infinity. The magnifying power in both cases will be
If F o and F e are the focal length of the objective and eye-piece respectively of a telescope, then its magnifying power will be
An astronomical telescope has an angular magnification of magnitude 5 for distant objects. The separation between the objective and the eye piece is 36 cm and the final image is formed at infinity. The focal length f o of the objective and the focal length f e of the eye piece are
The focal length of the objective and eye piece of a telescope are respectively 60 cm and 10 cm. The magnitude of the magnifying power when the image is formed at infinity is
If the telescope is reversed i.e. seen from the objective side
An opera glass (Gallilean telescope) measures 9 cm from the objective to the eyepiece. The focal length of the objective is 15 cm. Its magnifying power is
Relative difference of focal lengths of objective and eye lens in the microscope and telescope is given as
In an astronomical telescope, the focal length of the objective lens is 100 cm and of eye-piece is 2 cm. The magnifying power of the telescope for the normal eye is
A photograph of the moon was taken with telescope. Later on, it was found that a housefly was sitting on the objective lens of the telescope. In photograph
A Gallilean telescope has objective and eye-piece of focal lengths 200 cm and 2 cm respectively. The magnifying power of the telescope for normal vision is
The magnifying power of an astronomical telescope is 8 and the distance between the two lenses is 54 cm. The focal length of eye lens and objective lens will be respectively
In Gallilean telescope, the final image formed is
The magnifying power of a telescope is 9. When it is adjusted for parallel rays, the distance between the objective and the eye-piece is found to be 20 cm. The focal length of the two lenses are
On which of the following does the magnifying power of a telescope depends
A reflecting telescope utilizes
The length of a telescope is 36 cm. The focal lengths of its lenses can be
In a laboratory four convex lenses L 1 , L 2 , L 3 and L 4 of focal lengths 2, 4, 6 and 8 cm respectively are available. Two of these lenses form a telescope of length 10 cm and magnifying power 4. The objective and eye lenses are
To increase both the resolving power and magnifying power of a telescope.
A telescope has an objective of focal length 50 cm and an eye piece of focal length 5 cm. The least distance of distinct vision is 25 cm. The telescope is focussed for distinct vision on a scale 200 cm away. The separation between the objective and the eye-piece is
In an astronomical telescope, the focal length of objective lens and eye-piece are 150 cm and 6 cm respectively. In case when final image is formed at least distance of distinct vision. the magnifying power is
Four lenses of focal length + 15 cm, + 20cm, + 150cm and + 250 cm are available for making an astronomical telescope. To produce the largest magnification, the focal length of the eye-piece should be
A terrestrial telescope is made by introducing an erecting lens of focal length f between the objective and eye piece lenses of an astronomical telescope. This causes the length of the telescope tube to increase by an amount equal to
In a terrestrial telescope, the focal length of objective is 90 cm, of inverting lens is 5cm and of eye lens is 6 cm. If the final image is at 30 cm, then the magnification will be
A Galileo telescope has an objective of focal length 100 cm and magnifying power 50. The distance between the two lenses in normal adjustment will be
If both the object and image are at infinite distances form a refracting telescope its magnifying power will be equal to
For a compound microscope, the focal lengths of object lens and eye lens are f o and f e respectively, then magnification will be done by microscope when
Magnification of a compound microscope is 30. Focal length of eye-piece is 5 cm and the image is formed at a distance of distinct vision of 25 cm. The magnification of the objective lens is
A Galileo telescope has an objective of focal length 100 cm and magnifying power 50. The distance between the two lenses in normal adjustment will be
Which of the following is not correct regarding the radio telescope
A point object is placed at the centre of a glass sphere of diameter 12 cm and refractive index 1.5. What is the distance of the virtual image from the surface of the sphere?
A person can see clearly only up to a distance of 30 cm. He wants to read a book placed at a distance of 50 cm from his eyes. What is the power of the lens he requires for his spectacles?
To an astronaut in a spaceship, the sky appears
The image of an object, formed by a plano-convex lens at a distance of 8 m behind the lens, is real and is one-third the size of the object. The wavelength of light inside the lens is 2/3 times and the wavelength in free space. The radius of the curved surface of the lens is
A prism of refractive index 2 has angle of prism 30 0 . One of the refracting surface of prism is silvered. Find the angle of incidence i for which the ray retraces its path
An object AB of height 2 cm is placed at distance 63 cm from a concave mirror of radius of curvature 40 cm. A slab of refractive index 4 3 and thickness 12 cm is placed between the object and the mirror.
A point source of light S is placed at distance 10 cm from the pole of a convex mirror of local length 10 cm. The intensity of light at the center of screen in the absence of mirror is 49 W m − 2 . Find the intensity of light on screen in the presence of mirror.
When an object is at distance 10 cm and 30 cm from a thin converging lens, virtual and real image of same size is formed. The power of lens is
At the mouth of a cylindrical vessel, a convex lens of refractive index 1.5 and radius of curvature of curved surface 30 cm is filled. A point source S is at the bottom of vessel. The height of vessel is 40 cm and filled with liquid of refractive index 1.2. Find the position of image.
For the situation as shown in the figure, find the velocity of image formed by the mirror
In the situation as shown in the figure, the focal length of the thin plane concave lens is 20 cm. A point object P is at distance of 20 cm from the lens. Find the velocity of image formed by plane mirror at the instant as shown in the figure.
Two thin prism each of single of prism 5 0 and refractive index 1.5 are combined base to base as shown in the figure. Find separation between images formed due to refraction through prisms.
The refracting angle of prism is 14 11 0 and refractive index is 1.5. A thin convex lens of focal length 20 cm is placed at distance 30 cm from the point source S as shown in figure. The position of image of point source S is
There are two thin symmetrical lenses, one is converging with refractive index 2 and the other is diverging with refractive index 1.5. Both lenses have the same radius of curvature of 10 cm. The lenses were put close together and submerged into water. What is the focal length of the system in water?. The refractive index of water is 4 3
A point object P (at distance of 15 cm from lens) is approaching towards a thin and silvered equiconvex lens of local length 20 cm and refractive index 1.5 with a speed of 4 c m s − 1 as shown in figure. Find velocity of image.
The refractive index of medium of a rectangular slab varies as μ = 1 + γ . The ray enter from air to slab at origin in the condition of grazing incidence. The trajectory of ray inside slab is
The aperture radius of thin convex lens is 2 mm. Find the radius of circular bright spot on screen
The figure shows the initial position of a point source of light S (100 cm away from lens), a detector D and a lens L. Now at t = 0, all the three start moving towards right with different velocities as shown. The time(s) at which the detector receives the maximum light is (velocity of lens is 10cm s – 1 )
A point object is placed at the centre of a glass sphere of radius 6 cm and refractive index 1.5. The distance of the virtual image from the surface of the sphere is
A cube of side length 1 mm is placed at distance 30 cm from the pole of a concave mirror of focal length 20 cm. Its one side is parallel optical axis as shown in the figure. Find the magnification in the volume of cube
A circular plane mirror is placed on a table and a hemisphere of radius 10 cm is placed on it. The center of hemisphere is at the center of mirror. The minimum radius of circular mirror for which image of point object P is formed by the mirror is?
The focal length of an objective of a telescope is 3 metre and diameter 15 cm. Assuming for a normal eye, the diameter of the pupil is 3 mm for its complete use, the focal length of eye piece must be
In an astronomical telescope in normal adjustment, a straight black line of length L is drawn on the objective lens. The eyepiece forms a real image of this line. The length of this image is l. The magnification of the telescope is
If the focal length of objective and eye lens are 1.2 cm and 3 cm respectively and the object is put 1.25cm away from the objective lens and the final image is formed at infinity. The magnifying power of the microscope is
If the tube length of astronomical telescope is 105cm and magnifying power is 20 for normal setting, calculate the focal length of the objective lens
A plano-convex lens fits exactly into a plano-concave lens. Their plane surface are parallel to each other. If the lenses are made of different material of refractive indices μ 1 and μ 2 and R is the radius of curvature of the curved surface of the lenses, then focal length of the combination is
Light is incident normally on face AB of a prism as shown in Figure. A liquid of refractive index μ is placed on face AC of the prism. The prism is made of glass of refractive index 3/2. The limit of μ for which total internal reflection takes place at face AC is
A ray of light enters a rectangular glass slab of refractive index 3 at an angle of incidence 60 0 . It travels a distance of 5cm inside the slab and emerges out of the slab. The perpendicular distance between the incident and the emergent rays is
In the given figure, the image of object AB observed by observer is
A point object is placed in front of a thick plane mirror as shown in Figure. Find the location of final image w.r.t. object.
A rectangular block of glass is placed on a printed page lying on a horizontal surface. The minimum value of the refractive index of glass for which the letters on the page are not visible from any of the vertical faces of block is
The curve of angle of incidence versus angle of deviation shown has been plotted for prism. The value of refractive index of the equilateral prism used is
A circular beam of light of diameter d = 2cm falls on a plane surface of glass. The angle of incidence is 60 0 and refractive index of glass is μ = 3 / 2 . The diameter of the refracted beam is
Two identical μ g = 3 / 2 equiconvex lenses of focal length f are kept in contact. The space between the two lenses is filled with water μ ω = 4 / 3 . The focal length of the combination is
A small piece of wire bent into an L shape, with upright and horizontal portions of equal lengths, is placed with the horizontal portion along the axis of the concave mirror whose radius of curvature is 10 cm. If the bend is 20 cm from the pole of the mirror, then the ratio of the lengths of the images of the upright and horizontal portions of the wire is
A convex lens of focal length 10 cm is painted back at the middle portion as shown in figure. An object is placed at a distance of 20 cm from the lens. Then,
A linear object AB is placed along the axis of a concave mirror. The object is moving towards the mirror with speed u. The speed of the image of the point A is 4u and the speed of the image of B is also 4u but in opposite direction. If the centre of the line AB is at a distance L from the mirror then find out the length of the object.
A thin lens of refractive index 1.5, and focal length in air 20 cm is placed inside, a large container containing two immiscible liquids as shown below. If an object is placed at an infinite distance close to principle axis (common intersection line of layers), the distance between images
A convex lens of focal length 40 cm is held coaxially above mirror of focal length 18 cm. A luminous point object placed d cm above the lens on its axis gives rise to final image coincident with itself. Then d is equal to
An insect of negligible mass is sitting on a block of mass M, tied with a spring of force constant K. The block performs simple harmonic motion with amplitude A in front of a plane mirror placed as shown. The maximum speed of insect relative to its image will be
A man is standing on a straight road in a summer noon. The refractive index of the air changes with height as μ = μ o 1 + y 3 m e t e r due to variation of the vertical temperature where μ o is the refractive index of the air at road surface and y height. Eyes of the man are at height of 1.5 m above the road. What is the apparently visible length of the road?
A ray of light is incident on a plane mirror, along the direction given by, A = 2 i ^ − 3 j ^ + 4 k ^ . Find the unit vector along the reflected ray. Take normal to mirror along the direction of B = 3 i ^ − 6 j ^ + 2 k ^
Two mirrors are placed at right angles to each other. A man is standing between them combing his hair. How many image will he see?
In a room containing smoke particles, the intensity due to a source of light will :
A parallel beam of light is incident on a converging lens parallel to its principal axis. As one moves away from the lens on the other side on its principal axis, the intensity of light
Two thin lenses of focal lengths f 1 and f 2 are made of materials of dispersive powers ω 1 and ω 2 respectively. The lenses are kept in contact. The combination will show no chromatic aberration if
A narrow beam of white light goes through a slab having parallel faces
A lens is placed between a source of light and a wall. It forms images of area A 1 and A 2 on the wall for its two different positions. The area of the source of light is
If f V and f R are the magnitude of focal lengths of a convex lens for violet and red light respectively and F V and f R are the magnitude of focal lengths of concave lens for violet and red light respectively, then we have
A ray of light from a denser medium strike a rarer medium at an angle of incidence i. The reflected and refracted rays make an angle of 90 0 with each other. The angles of reflection and refraction are r and r ‘ . The critical angle is
If a glass prism is dipped in water, its dispersive power
The converging point of incident beam is at the 20 cm from concave lens as shown in the figure are. The concave lens then moved away from convex lens with speed 1 c m s − 1 . The emergent ray from convex lens is
Smoke emerging from a campfire at the bottom of a hill is being observed by a person at some distance, as shown in the figure. It is evening and the sun has just set behind the hill. Consider regions I and II of the smoke going up the sky
The image formed by an objective of a compound microscope is
The figure shows different graphs in case of a thin convex lens for the formation of a real image, u and v are the object and image distances respectively. Find out the correct identification for the different combinations from the following.
A compound microscope is used to enlarge an object kept at a distance 0.03 m from it’s objective which consists of several convex lenses in contact and has focal length 0.02 m . If a lens of focal length 0.1 m is removed from the objective, then by what distance the eye-piece of the microscope must be moved to refocus the image (in cm)
A hollow cylinder has diameter 10 cm and height 8.64 cm. When vessel is empty, observer E can see the point mark A. If vessel is filled with a liquid, he can see the point mark at the center. Find the refractive index of liquid.
A sphere of refractive index μ = 2 has inner radius 10 cm and outer radius 20 cm. It is placed in air as shown in the figure. The distance through which point mark P appear to shift is ……. cm.
A solid glass sphere of radius 10 cm and refractive index 3 2 is placed in a medium of refractive index μ = 2 . The hemispherical portion of the sphere is silvered. A point object P is placed at distance 30 cm from the centre of sphere. The distance of final image of point object P from center of sphere is 50 n 11 cm. Find the value of n.
A ray of light is incident at an angle of 60 0 on one face of a prism which has refracting angle of 30 0 . The ray emerging out of the prism makes an angle of 30 0 with the incident ray. Find the value of refractive index of the material of the prism .
A convex lens of focal length f cut into parts first horizontally and then vertically. If the focal length of part A (quarter part) of the lens is xf , then x is
A ray of light falls on transparent sphere with centre at C as shown in the figure. The ray emerges from the sphere parallel to the line AB. The refractive index of the sphere is x then x is
Refraction of light from air to glass and from air to water are shown in figure (i) and (ii) below. The value of the angle in the case of refraction as shown in figure (iii) will be
A lens having focal length f and aperture of diameter d forms an image of intensity I . Aperture of diameter d 2 in central region of lens is covered by a black paper. Focal length of lens and intensity of image now will be respectively:
If we need a magnification of 375 from a compound microscope of tube length 150 mm and an objective of focal length 5mm, the focal length of the eye-piece, should be close to :
A thin lens made of glass (refractive index = 1.5) of focal length f = 16 cm is immersed in a liquid of refractive index 1.42. If its focal length in liquid is f 1 then the ratio f 1 / f is closest to the integer:
The critical angle of a medium for a specific wavelength, if the medium has relative permittivity 3 and relative permeability 4 3 for this wavelength, will be:
The magnifying power of a telescope with tube length 60cm is 5. What is the focal length of its eye piece?
An object is gradually moving away from the focal point of a concave mirror along the axis of the mirror. The graphical representation of the magnitude of linear magnification (m) versus distance of the object from the mirror(x) is correctly given by (Graphs are drawn schematically and are not to scale)
A vessel of depth 2h is half filled with a liquid of refractive index 2 2 and the upper half with another liquid of refractive index 2 . The liquids are immiscible. The apparent depth of the inner surface of the bottom of vessel will be :
A spherical mirror is obtained as shown in the figure from a hollow glass sphere. If an object is positioned in front of the mirror, what will be the nature and magnification of the image of the object? (Figure drawn as schematic and not to scale)
A light ray enters a solid glass sphere of refractive index μ = 3 at an angle of incidence 60 0 . The ray is both reflected and refracted at the farther surface of the sphere. The angle (in degrees) between the reflected and refracted rays at this surface is
An observer can see through a small hole on the side of a jar (radius 15 cm) at a point at height of 15 cm from the bottom (see figure). The hole is at a height of 45 cm. When the jar is filled with a liquid up to a height of 30 cm the same observer can see the edge at the bottom of the jar. If the refractive index of the liquid is N/100, where N is an integer, the value of N is
When an object is kept at a distance of 30cm from a concave mirror, the image is formed at a distance of 10 cm from the mirror. If the object is moved with a speed of 9 cm s – 1 , the speed (in cm s – 1 ) with which image moves at the instant is
In a compound microscope, the magnified virtual image is formed at a distance of 25 cm from the eye-piece. The focal length of its objective lens is 1 cm. If the magnification is 100 and the tube length of the microscope is 20 cm, then the focal length of the eye-piece lens (in cm) is .
The distance between an object and a screen is 100 cm. A lens can produce real image of the object on the screen for two different positions between the screen and the object. The distance between these two positions is 40 cm. If the power of the lens is close to N 100 D where N is an integer, the value of N is
For a concave lens of focal length f , the relation between object and image distances u and ν ,respectively, from its pole can best be represented by ( u = ν is the reference line):
A compound microscope consists of an objective lens of focal length 1 c m and an eye piece of focal length 5 c m with a separation of 10 c m . The distance between an object and the objective lens,at which the strain on the eye is minimum is n 40 . The value of n is
The focal lengths of the objective and the eye –piece of a compound microscope are 2.0cm and 3.0cm respectively. The distance between the objective and the eye-piece is 15.0cm. The final image formed by the eye –piece is at infinity. The two lenses are thin. The distance in cm of the object and the image produced by the objective measured from the objective lens are respectively. (in cm)
When a real object is placed at 25cm from a lens, a real image is formed. Mark the Incorrect statement from the following
A compound microscope is used to enlarge an object kept at a distance 0.03m from its objective which consists of several convex lenses in contact and has focal length 0.02m. If a lens of focal length 0.1m is removed from the objective, find out the distance by which the eye piece of the microscope must be moved to refocus the image.
Mirror is moving towards the particles (negative x-axis) with speed 2cm/sec. Particles A and B are moving with speeds of 10 2 cm / sec and 5 cm / sec respectively in the direction shown in figure. Magnitude of velocity of image of the particle B with respect to image of A is
A certain prism is found to produce a minimum deviation of 38 ∘ . It produces a deviation of 44 ° when the angle of incidence is either 42 ° or 62 ° . What will be the angle of incidence when it undergoes minimum deviation?
The figure shows the initial position of a point source of light S, a detector D and Lens L. Now at t=0 all three start moving towards right with different velocities as shown in figure. The times at which detector receives the maximum light are (initially detector D is on lens as shown in figure.)
Two identical thin isosceles prisms of refracting angle ‘A’ and refractive index μ are placed with their bases touching each other. Two parallel rays of light are incident on this system as shown. The distance of the point where the rays converge from the prism is:
A light ray falls perpendicular on one face of an equilateral prism, having refractive index 3 . The angle of deviation is:
A glass sphere of radius R=10cm is kept inside water. A point object O is placed at 20cm from A as shown in figure then the position of the image formed due to refraction at the first surface is at p cm from A. The magnitude of p is……… Given μ g = 3 2 and μ ω = 4 3
A plano-convex lens, when silvered at its plane surface is equivalent to a concave mirror of focal length 28cm. When its curved surface is silvered and the plane surface not silvered, it is equivalent to a concave mirror of focal length 10cm, then the refractive index of the material of the lens is:
If a spherical mirror is immersed in a liquid, its focal length will:
A real, inverted and equal in size image is formed by:
In case of concave mirror, the minimum distance between a real object and its real image is:
The focal length of a spherical mirror is:
In case of spherical mirrors:
Which of the following (referred to a spherical mirror) depend on whether the rays are paraxial or not?
Variation of v with u for a spherical mirror is as shown in figure. This curve is a hyperbola. A straight line of unit slope intersects the hyperbola at point ‘A’. If the focal length of mirror is 20 cm, coordinates of point A are:
A plane mirror reflects a pencil of light to form a real image. Then the pencil of light incident on the mirror is
What should be the angle between two plane mirrors so that whatever be the angle of incidence, the incident ray and the reflected ray from the two mirrors be parallel to each other
Two vertical plane mirrors are inclined at an angle of 60° with each other. A ray of light travelling horizontally is reflected first from one mirror and then from the other. The resultant deviation is
A plane mirror is approaching you at a speed of 10 cm/sec. You can see your image in it. At what speed will your image approach you
A man is 180 cm tall and his eyes are 10 cm below the top of his head. In order to see his entire height right from toe to head, he uses a plane mirror kept at a distance of 1m from him. The minimum length of the plane mirror required is
A person is in a room whose ceiling and two adjacent walls are mirrors. How many images are formed?
A ray is reflected in turn by three plain mirrors mutually at right angles to each other. The angle between the incident and the reflected rays is
Two plane mirrors are at right angles to each other. A man stands between them and combs his hair with his right hand. In how many of the images will he be seen using his right hand
A plane mirror produces a magnification of
A watch shows time as 3 : 25 when seen through a mirror, time appeared will be
If an observer is walking away from the plane mirror with 6m/sec. Then the velocity of the image with respect to observer will be
A small object is placed 10 cm infront of a plane mirror. If you stand behind the object 30 cm from the mirror and look at its image, the distance focused for your eye will be
Two plane mirrors are inclined at an angle of 72°. The number of images of a point object placed between them will be
To get three images of a single object, one should have two plane mirrors at an angle of
A man having height 6 m. He observes image of 2 m height erect, then mirror used is
Two plane mirrors are at 45° to each other. If an object is placed between them, then the number of images will be
A light beam is being reflected by using two mirrors, as in a periscope used in submarines. If one of the mirrors rotates by an angle θ , the reflected light will deviate from its original path by the angle
Focal length of a plane mirror is
A ray of light is incident at 50° on the middle of one of the two mirrors arranged at an angle of 60° between them. The ray then touches the second mirror, get reflected back to the first mirror, making an angle of incidence of
A convex mirror of focal length f forms an image which is 1 n times the object. The distance of the object from the mirror is
A diminished virtual image can be formed only in
An object 5cm tall is placed 1m from a concave spherical mirror which has a radius of curvature of 20cm. The size of the image is
The focal length of a concave mirror is 50 cm. Where an object be placed so that its image is two times and inverted
An object of size 7.5cm is placed in front of a convex mirror of radius of curvature 25cm at a distance of 40cm. The size of the image should be
The field of view is maximum for
The focal length of a concave mirror is f and the distance from the object to the principle focus is x. The ratio of the size of the image to the size of the object is
Image formed by a convex mirror for a real object is
In a cave mirror experiment, an object is placed at a distance x 1 from the focus and the image is formed at a distance x 2 from the focus. The focal length of the mirror would be
The image formed by a convex mirror of focal length 30cm is a quarter of the size of the object. The distance of the object from the mirror is
Which one of the following statements is true
A person sees his virtual image by holding a mirror very close to the face. When he moves the mirror away from his face, the image becomes inverted. What type of mirror he is using
The relation between the linear magnification m, the object distance u and the focal length f for a spherical mirror is
While using an electric bulb, the reflection for street lighting should be from
An object is placed 40cm from a concave mirror of focal length 20 cm. The image formed is
An object is placed 40cm from a concave mirror of focal length 20 cm. The image formed is
A virtual image three times the size of the object is obtained with a concave mirror of radius of curvature 36cm. The distance of the object from the mirror is
All of the following statements are correct except
Radius of curvature of concave mirror is 40cm and the size of image is twice as that of object, then the object distance is
If an object is placed 10cm infront of a concave mirror of focal length 20cm, the image will be
A convex mirror has a focal length f. A real object is placed at a distance f in front of it from the pole produces an image at
An object 1cm tall is placed 4cm infront of a mirror. In order to produce an upright image of a 3cm height one needs a
The minimum distance between the object and its real image for concave mirror is
A point object is placed at a distance of 10cm and its real image is formed at a distance of 20 cm from a concave mirror. If the object is moved by 0.1cm towards the mirror, the image will shift by about
The focal length of a convex mirror is 20 cm its radius of curvature will be
A point object is placed at a distance of 30 cm from a convex mirror of focal length 30cm. The image will form at
An object 2.5 cm high is placed at a distance of 10 cm from a concave mirror of radius of curvature 30 cm. The size of the image is
For a real object, which of the following can produced a real image
An object of length 6 cm is placed on the principal axis of a concave mirror of focal length f at a distance of 4f. The length of the image will be
Convergence of concave mirror can be decreased by dipping in
Image formed by a concave mirror of focal length 6 cm, is 3 times of the object, then the distance of object from mirror is
Monochromatic light is refracted from air into the glass of refractive index. The ratio of the wavelength of incident and refracted waves is
Refractive index for a material for infrared light is
A beam of light propagating in medium A with index of refraction n (A) passes across an interface into medium B with index of refraction n(B). The angle of incidence is greater than the angle of refraction; v(A) and v(B) denotes the speed of light in A and B. Then which of the following is true
A rectangular tank of depth 8 meter is full of water ( μ = 4 3 ), the bottom is seen at the depth
A beam of light is converging towards a point I on a screen. A plane glass plate whose thickness in the direction of the beam = t, refractive index = μ , is introduced in the path of the beam. The convergence point is shifted by
Finger prints on a piece of paper may be detected by sprinkling fluorescent powder on the paper and then looking it into
Critical angle of light passing from glass to air is minimum for
The wavelength of light in two liquids ‘x’ and ‘y’ is 3500 Å and 7000 Å , then the critical angle of x relative to y will be
If the critical angle for total internal reflection from a medium to vacuum is 30°, the velocity of light in the medium is
A ray of light is incident at an angle i from denser to rare medium. The reflected and the refracted rays are mutually perpendicular. The angle of reflection and the angle of refraction are respectively r and r’, then the critical angle will be
For total internal reflection to take place, the angle of incidence i and the refractive index μ of the medium must satisfy the inequality
Total internal reflection of light is possible when light enters from
Total internal reflection of a ray of light is possible when the ( i c = critical angle, angle of incidence)
A diver at a depth of 12m in water ( μ = 4 3 ) sees the sky in a cone of semi-vertical angle
The critical angle for diamond (refractive index = 2) is
The refractive index of water is 4 3 and that of glass is 5 3 . What will be the critical angle for the ray of light entering water from the glass
The velocity of light in a medium is half its velocity in air. If ray of light emerges from such a medium into air, the angle of incidence, at which it will be totally internally reflected, is
Relation between critical angles of water and glass is
Brilliance of diamond is due to
White light is incident on the interface of glass and air as shown in the figure. If green light is just totally internally reflected then the emerging ray in air contains
Material A has critical angle i A and material B has critical angle i B i B > i A . Then which of the following is true (i) Light can be totally internally reflected when it passes from B to A (ii) Light can be totally internally reflected when it passes from A to B (iii) Critical angle for total internal reflection is i B − i A (iv) Critical angle between A and B is sin − 1 sini A sini B
Critical angle for light going from medium (i) to (ii) is θ . The speed of light in medium (i) is v then speed in medium (ii) is
An endoscope is employed by a physician to view the internal parts of a body organ. It is based on the principle of
A fish looking up through the water sees the outside world contained in a circular horizon. If the refractive index of water is 4 3 and the fish is 12 cm below the surface, the radius of this circle in cm is
A point source of light is placed 4 m below the surface of water of refractive index 5 3 . The minimum diameter of a disc which should be placed over the source on the surface of water to cut–off all light coming out of water is
A convex lens of focal length f is placed somewhere in between an object and a screen. The distance between the object and the screen is x. If the numerical value of the magnification produced by the lens is m, then the focal length of the lens is
A convex lens of focal length 40 cm is in contact with a concave lens of focal length 25 cm. The power of combination is
Two lenses are placed in contact with each other and the focal length of combination is 80 cm. If the focal length of one is 20 cm, then the power of the other will be
Two lenses of power +12 and – 2 diopters are placed in contact. What will the focal length of combination?
If in a plano-convex lens, the radius of curvature of the convex surface is 10 cm and the focal length of the lens is 30 cm, then the refractive index of the material of lens will be
The slit of a collimator is illuminated by a source as shown in the adjoining figures. The distance between the slit S and the collimating lens L is equal to the focal length of the lens. The correct direction of the emergent beam will be as shown in figure
A convex lens of focal length 84 cm is in contact with a concave lens of focal length 12 cm. The power of combination (in diopters) is
A convex lens makes a real image 4 cm long on a screen. When the lens is shifted to a new position without disturbing the object, we again get a real image on the screen which is 16 cm tall. The length of the object must be
A glass convex lens μ g = 1 .5 has a focal length of 8 cm when placed in air. What would be the focal length of the lens when it is immersed in water ( μ w = 1 .33 ) ?
The ray diagram could be correct
A convex lens of crown glass ( n =1.525) will behave as a divergent lens if immersed in
A divergent lens will produce
The minimum distance between an object and its real image formed by a convex lens is
An object is placed at a distance of 20 cm from a convex lens of focal length 10 cm. The image is formed on the other side of the lens at a distance
Two thin lenses, one of focal length + 60 cm and the other of focal length – 20 cm are put in contact. The combined focal length is
Two thin lenses of focal lengths 20 cm and 25 cm are placed in contact convex. The effective power of the combination is
A double convex thin lens made of glass (refractive index μ = 1.5) has both radii of curvature of magnitude 20 cm. Incident light rays parallel to the axis of the lens will converge at a distance L such that
A biconvex lens forms a real image of an object placed perpendicular to its principal axis. Suppose the radii of curvature of the lens tend to infinity. Then the image would
The radius of curvature of convex surface of a thin plano-convex lens is 15 cm and refractive index of its material is 1.6. The power of the lens will be
A lens is placed between a source of light and a wall. It forms images of area A 1 and A 2 on the wall for its two different positions. The area of the source or light is
Two lenses of power 6D and – 2D are combined to form a single lens. The focal length of this lens will be
An achromatic combination of lenses is formed by joining
A combination of two thin lenses with focal lengths f 1 and f 2 respectively forms an image of distant object at distance 60 cm when lenses are in contact. The position of this image shifts by 30 cm towards the combination when two lenses are separated by 10 cm. The corresponding values of f 1 and f 2 are
A diminished image of an object is to be obtained on a screen 1.0 m from it. This can be achieved by appropriately placing
The focal length of convex lens is 30 cm and the size of image is quarter of the object, then the object distance is
A convex lens forms a real image of a point object placed on its principal axis. If the upper half of the lens is painted black, the image will
In the figure, an air lens of radii of curvature 10 cm R 1 = R 2 = 10 cm is cut in a cylinder of glass, ( μ = 1 .5 ) . The focal length and the nature of the lens is
A lens (focal length 50 cm) forms the image of a distant object which subtends an angle of 1 milliradian at the lens. What is the size of the image?
Two thin lenses of focal lengths f 1 and f 2 are in contact and coaxial. The combination is equivalent to a single lens of power
A plano convex lens is made of glass of refractive index 1.5. The radius of curvature of its convex surface is R. Its focal length is
The dispersive powers of glasses of lenses used in an achromatic pair are in the ratio 5 : 3. If the focal length of the concave lens is 15 cm then the nature and focal length of the other lens would be
The plane surface of a plano-convex lens of focal length f is silvered. It will behave as
An object of height 1.5 cm is placed on the axis of a convex lens of focal length 25 cm. A real image is formed at a distance of 75 cm from the lens. The size of the image will be
A symmetric double convex lens is cut in two equal parts by a plane perpendicular to the principal axis. If the power of the original lens was 4 D, the power of a cut lens will be
A planoconvex lens is made of refractive index 1.6. The radius of curvature of the curved surface is 60 cm. The focal length of the lens is
A concave lens of glass, refractive index 1.5, has both surfaces of same radius of curvature R. On immersion in a medium of refractive index 1.75, it will behave as a
A convex lens of focal length 0.5 m and concave lens of focal length 1 m are combined. The power of the resulting lens will be
A double convex lens is made of glass of refractive index 1.5. If its focal length is 30 cm, then radius of curvature of each of its curved surface is
A thin lens made of glass of refractive index 1.5 has a front surface + 11 D power and back surface – 6 D. If this lens is submerged in a liquid of refractive index 1.6, the resulting power of the lens is
An object is placed first at infinity and then at 20 cm from the object side focal plane of the convex lens. The two images thus formed are 5 cm apart. The focal length of the lens is
The distance between an object and the screen is 100 cm. A lens produces an image on the screen when placed at either of the positions 40 cm apart. The power of the lens is
The image distance of an object placed 10 cm in front of a thin lens of focal length + 5 cm is
A achromatic combination is made with a lens of focal length and dispersive power ω with a lens having dispersive power of 2 ω . The focal length of second will be
A convex lens
A biconvex lens with equal radii curvature has refractive index 1.6 and focal length 10 cm. Its radius of curvature will be
The focal length of a combination of lenses formed with lenses having powers of + 2.50 D and – 3.75 D will be
Focal length of a converging lens in air is R. If it is dipped in water of refractive index 1.33, then its focal length will be around (Refractive index of lens material is 1.5)
Focal length of a convex lens of refractive index 1.5 is 2 cm. Focal length of lens when immersed in a liquid of refractive index of 1.25 will be
The focal length of a convex lens depends upon
If a convex lens of focal length 80 cm and a concave lens of focal length 50 cm are combined together, what will be their resulting power
f v and f r are the focal lengths of a convex lens for violet and red light respectively and F v and F r are the focal lengths of a concave lens for violet and red light respectively, then
If a lens is cut into two pieces perpendicular to the principal axis and only one part is used, the intensity of the image
A convex lens of focal length f produces a real image 1 n times than that of the size of the object. The distance of the object from the lens is
Two thin lenses whose powers are +2D and –4D respectively combine, then the power of combination is
A substance is behaving as convex lens in air and concave in water, then its refractive index is
A concave lens of focal length 20 cm placed in contact with a plane mirror acts as a
A convex lens is used to form real image of an object on a screen. It is observed that even when the positions of the object and that screen are fixed there are two positions of the lens to form real images. If the heights of the images are 4 cm and 9 cm respectively, the height of the object is
A convex lens of power + 6D is placed in contact with a concave lens of power – 4D. What is the nature and focal length of the combination
A double convex lens of glass of μ = 1.5 has radius of curvature of each of its surface is 0.2 m. The power of the lens is
A lens of focal power 0.5 D is
A lens which has focal length of 4 cm and refractive index of 1.4 is immersed in a liquid of refractive index 1.6, then the focal length will be
A convex lens has 9 cm focal length and a concave lens has – 18 cm focal length. The focal length of the combination in contact will be
A double convex thin lens made of glass of refractive index 1.6 has radii of curvature 15 cm each. The focal length of this lens when immersed in a liquid of refractive index 1.63 is
A lens of power + 2 diopters is placed in contact with a lens of power – 1 diopoter. The combination will behave like
Chromatic aberration of lens can be corrected by
The relation between n 1 and n 2 , if behaviour of light rays is as shown in figure is
A candle placed 25 cm from a lens, forms an image on a screen placed 75 cm on the other end of the lens. The focal length and type of the lens should be
In a plano-convex lens the radius of curvature of the convex lens is 10 cm. If the plane side is polished, then the focal length will be (Refractive index = 1.5)
We combined a convex lens of focal length f 1 and concave lens of focal lengths f 2 and their combined focal length was F. The combination of these lenses will behave like a concave lens, if
The focal length of a convex lens is 10 cm and its refractive index is 1.5. If the radius of curvature of one surface is 7.5 cm, the radius of curvature of the second surface will be
A convex lens has a focal length f. It is cut into two parts along the dotted line as shown in the figure. The focal length of each part will be
An object has image thrice of its original size when kept at 8 cm and 16 cm from a convex lens. Focal length of the lens is
The combination of a convex lens (f = 18 cm) and a thin concave lens (f = 9 cm) is
A convex lens forms a real image of an object for its two different positions on a screen. If height of the image in both the cases be 8 cm and 2 cm, then height of the object is
The unit of focal power of a lens is
A convex lens of focal length 25 cm and a concave lens of focal length 10 cm are joined together. The power of the combination will be
A thin lens made of glass of refractive index μ = 1.5 has a focal length equal to 12 cm in air. It is now immersed in water μ = 4 3 . Its new focal length is
Figure given below shows a beam of light converging at point P. When a concave lens of focal length 16 cm is introduced in the path of the beam at a place O shown by dotted line such that OP becomes the axis of the lens, the beam converges at a distance x from the lens. The value x will be equal to
A convex lens produces a real image m times the size of the object. What will be the distance of the object from the lens?
If two + 5 D lenses are mounted at some distance apart, the equivalent power will always be negative if the distance is
A convex lens is made up of three different materials as shown in the figure. For a point object placed on its axis, the number of images formed are
An object is placed 12 cm to the left of a converging lens of focal length 8 cm. Another converging lens of 6 cm focal length is placed at a distance of 30 cm to the right of the first lens. The second lens will produce
If convex lens of focal length 80cm and a concave lens of focal length 50 cm are combined together, what will be their resulting power
A point object O is placed in front of a glass rod having spherical end of radius of curvature 30 cm. The image would be formed at
Two thin lenses of focal lengths f 1 and f 2 are in contact. The focal length of this combination is
A convex lens is dipped in a liquid whose refractive index is equal to the refractive index of the lens. Then its focal length will
An equiconvex lens is cut into two halves along (i) XOX ‘ and (ii) YOY ‘ as shown in the figure. Let f, f ‘ , f ” be the focal lengths of the complete lens, of each half in case (i), and of each half in case (ii), respectively Choose the correct statement from the following
The sun makes 0.5 o angle on earth surface. Its image is made by convex lens of 50 cm focal length. The diameter of the image will be
The chromatic Aberration in lenses becomes due to
If aperture of lens is halved then image will be
When the convergent nature of a convex lens will be less as compared with air
An object placed 10 cm in front of a lens has an image 20 cm behind the lens. What is the power of the lens (in dioptres)?
A beam of parallel rays is brought to a focus by a plano-convex lens. A thin concave lens of the same focal length is joined to the first lens. The effect of this is
In order to obtain a real image of magnification 2 using a converging lens of focal length 20 cm, where should an object be placed
A point object is placed at the center of a glass sphere of radius 6 cm and refractive index 1.5. The distance of the virtual image from the surface of the sphere is
A double convex lens R 1 = R 2 = 10 cm ( μ = 1 .5 ) having focal length equal to the focal length of a concave mirror. The radius of curvature of the concave mirror is
Spherical aberration in a lens
A bi-convex lens made of glass (refractive index 1.5) is put in a liquid of refractive index 1.7. Its focal length will
The focal lengths for violet, green and red light rays are f V , f G and f R respectively. Which of the following is the true relationship
The plane faces of two identical plano-convex lenses each having focal length of 40 cm are pressed against each other to form a usual convex lens. The distance from this lens, at which an object must be placed to obtain a real, inverted image with magnification one is
If two lenses of +5 diopters are mounted at some distance apart, the equivalent power will always be negative if the distance is
A combination of two thin lenses of the same material with focal lengths f 1 and f 2 , arranged on a common axis minimizes chromatic aberration, if the distance between them is
If the focal length of a double convex lens for red light is f R , its focal length for the violet light is
A thin equiconvex lens is made of glass of refractive index 1.5 and its focal length is 0.2 m, if it acts as a concave lens of 0.5 m focal length when dipped in a liquid, the refractive index of the liquid is
The dispersive power of the material of lens of focal length 20 cm is 0.08. The longitudinal chromatic aberration of the lens is
Formula for dispersive power is (where symbols have their usual meanings) or If the refractive indices of crown glass for red, yellow and violet colours are respectively μ r , μ y and μ v , then the dispersive power of this glass would be
We use flint glass prism to disperse polychromatic light because light of different colours
When white light passes through a glass prism, one gets spectrum on the other side of the prism. In the emergent beam, the ray which is deviating least is or Deviation by a prism is lowest for
The critical angle between an equilateral prism and air is 45°. If the incident ray is perpendicular to the refracting surface, then
Fraunhofer lines are obtained in
When light rays are incident on a prism at an angle of 45°, the minimum deviation is obtained. If refractive index of the material of prism is 2 , then the angle of prism will be
A spectrum is formed by a prism of dispersive power ‘ ω ′ . If the angle of deviation is ‘ δ ′ , then the angular dispersion is
Angle of minimum deviation for a prism of refractive index 1.5 is equal to the angle of prism. The angle of prism is (cos 41° = 0.75)
In the formation of primary rainbow, the sunlight rays emerge at minimum deviation from rain-drop after
Dispersive power depends upon
When white light passes through the achromatic combination of prisms, then what is observed
The refractive index of a prism for a monochromatic wave is 2 and its refracting angle is 60°. For minimum deviation, the angle of incidence will be
The ratio of angle of minimum deviation of a prism in air and when dipped in water will be a μ g = 3 / 2 and a μ w = 4 / 3
The respective angles of the flint and crown glass prisms are A’ and A. They are to be used for dispersion without deviation, then the ratio of their angles A’ /A will be
The black lines in the solar spectrum during solar eclipse can be explained by
The dispersive power is maximum for the material
A light ray is incident by grazing one of the face of a prism and after refraction ray does not emerge out, what should be the angle of prism while critical angle is C
Three prisms of crown glass, each have angle of prism 9° and two prisms of flint glass are used to make direct vision spectroscope. What will be the angle of flint glass prisms if μ for flint is 1.60 and μ for crown glass is 1.53
If the refractive indices of crown glass for red, yellow and violet colours are 1.5140, 1.5170 and 1.5318 respectively and for flint glass these are 1.6434, 1.6499 and 1.6852 respectively, then the dispersive powers for crown and flint glass are respectively
The minimum temperature of a body at which it emits light is
Flint glass prism is joined by a crown glass prism to produce dispersion without deviation. The refractive indices of these for mean rays are 1.602 and 1.500 respectively. Angle of prism of flint prism is 10°, then the angle of prism for crown prism will be
The angle of minimum deviation for a prism is 40° and the angle of the prism is 60°. The angle of incidence in this position will be
In the position of minimum deviation when a ray of yellow light passes through the prism, then its angle of incidence is
The fine powder of a coloured glass is seen as
When a white light passes through a hollow prism, then
The light ray is incidence at angle of 60° on a prism of angle 45°. When the light ray falls on the other surface at 90°, the refractive index of the material of prism μ and the angle of deviation δ are given by
In dispersion without deviation
Deviation of 5° is observed from a prism whose angle is small and whose refractive index is 1.5. The angle of prism is
If the refractive indices of a prism for red, yellow and violet colours be 1.61, 1.63 and 1.65 respectively, then the dispersive power of the prism will be
The angle of minimum deviation measured with a prism is 30° and the angle of prism is 60°. The refractive index of prism material is
For a material, the refractive indices for red, violet and yellow colour light are respectively 1.52, 1.64 and 1.60. The dispersive power of the material is
A medium is said to be dispersive, if
Fraunhofer lines are produced by
A ray of light is incident at an angle of 60° on one face of a prism of angle 30°. The ray emerging out of the prism makes an angle of 30° with the incident ray. The emergent ray is
In a thin prism of glass (refractive index 1.5), which of the following relations between the angle of minimum deviations δ m and angle of refraction r will be correct
A ray of light passes through an equilateral glass prism in such a manner that the angle of incidence is equal to the angle of emergence and each of these angles is equal to 3 4 of the angle of the prism. The angle of deviation is
The true statement is
What will be the colour of sky as seen from the earth, if there were no atmosphere
A prism ABC of angle 30° has its face AC silvered. A ray of light incident at an angle of 45° at the face AB retraces its path after refraction at face AB and reflection at face AC. The refractive index of the material of the prism is
A light ray is incident upon a prism in minimum deviation position and suffers a deviation of 34°. If the shaded half of the prism is knocked off, the ray will
A ray of monochromatic light is incident on one refracting face of a prism of angle 75°. It passes through the prism and is incident on the other face at the critical angle. If the refractive index of the material of the prism is 2 , the angle of incidence (in degree) on the first face of the prism is
The refractive index of a material of a prism of angles 45°– 45° – 90° is 1.5. The path of the ray of light incident normally on the hypotenuse side is shown in
At the time of total solar eclipse, the spectrum of solar radiation would be
Angle of deviation ( δ ) by a prism (refractive index = μ and supposing the angle of prism A to be small) can be given by
At sun rise or sunset, the sun looks more red than at mid-day because
When light of wavelength λ is incident on an equilateral prism kept in its minimum deviation position, it is found that the angle of deviation equals the angle of the prism itself. The refractive index of the material of the prism for the wavelength λ is, then
The refractive index of flint glass for blue F line is 1.6333 and red C line is 1.6161. If the refractive index for yellow D line is 1.622, the dispersive power of the glass is
White light is passed through a prism whose angle is 5°. If the refractive indices for rays of red and blue colour are respectively 1.64 and 1.66, the angle of deviation between the two colours will be
If the refractive index of a material of equilateral prism is 3 , then angle of minimum deviation of the prism is
Two lenses having f 1 : f 2 = 2 : 3 has combination to make no dispersion. Find the ratio of dispersive power of glasses used
A ray is incident at an angle of incidence i on one surface of a prism of small angle A and emerges normally from the opposite surface. If the refractive index of the material of the prism is μ , the angle of incidence i is nearly equal to
The angle of a prism is 60° and its refractive index is 2 . The angle of minimum deviation suffered by a ray of light in passing through it is
Which of the following colours suffers maximum deviation in a prism
If a thin prism of glass is dipped into water then minimum deviation (with respect to air) of light produced by prism will be left aμ g = 3 2 and aμ w = 4 3
The refractive indices for the light of violet and red colours of any material are 1.66 and 1.64 respectively. If the angle of prism made of this material is 10°, then angular dispersion will be
Dispersion of light is due to
Dark lines on solar spectrum are due to
If refractive index of red, violet and yellow lights are 1.42, 1.62 and 1.50 respectively for a medium. Its dispersive power will be
The dispersive powers of crown and flint glasses are 0.02 and 0.04 respectively. In an achromatic combination of lenses the focal length of flint glass lens is 40 cm. The focal length of crown glass lens will be
For a medium, refractive indices for violet, red and yellow are 1.62, 1.52 and 1.55 respectively, then dispersive power of medium will be
When a ray of light is incident normally on one refracting surface of an equilateral prism (Refractive index of the material of the prism = 1.5)
Fraunhofer spectrum is a
Stars are not visible in the day time because
The nature of sun’s spectrum is
The angle of prism is 5° and its refractive indices for red and violet colours are 1.5 and 1.6 respectively. The angular dispersion produced by the prism is
If the refractive angles of two prisms made of crown glass are 10° and 20° respectively, then the ratio of their colour deviation powers will be
Under minimum deviation condition in a prism, if a ray is incident at an angle 30°, the angle between the emergent ray and the second refracting surface of the prism is
A ray of light is incident normally on one of the face of a prism of angle 30° and refractive index 2 . The angle of deviation will be
Three prisms 1, 2 and 3 have the prism angle A = 60°, but their refractive indices are respectively 1.4, 1.5 and 1.6. If δ 1 , δ 2 , δ 3 be their respective angles of deviation then
In the visible region the dispersive powers and the mean angular deviations for crown and flint glass prisms are ω , ω ′ and d , d ′ respectively. The condition for getting deviation without dispersion when the two prisms are combined is
A ray of light passes through the equilateral prism such that angle of incidence is equal to the angle of emergence if the angle of incidence is 45°. The angle of deviation will be
The Cauchy’s dispersion formula is
Three glass prisms A, B and C of same refractive index are placed in contact with each other as shown in figure, with no air gap between the prisms. Monochromatic ray of light OP passes through the prism assembly and emerges as QR. The conditions of minimum deviation is satisfied in the prisms
A given ray of light suffers minimum deviation in an equilateral prism P. Additional prisms Q and R of identical shape and material are now added to P as shown in the figure. The ray will suffer
In the given figure, what is the angle of prism
A prism of refractive index 2 has a refracting angle of 60°. At what angle a ray must be incident on it so that it suffers a minimum deviation
A parallel beam of white light falls on a convex lens. Images of blue, yellow and red light are formed on other side of the lens at a distance of 0.20 m, 0.205 m and 0.214 m respectively. The dispersive power of the material of the lens will be
The refractive index of a particular material is 1.67 for blue light, 1.65 for yellow light and 1.63 for red light. The dispersive power of the material is
A ray of light is incident on an equilateral glass prism placed on a horizontal table. For minimum deviation which of the following is true
A beam of light composed of red and green ray is incident obliquely at a point on the face of rectangular glass slab. When coming out on the opposite parallel face, the red and green ray emerge from
A ray of monochromatic light suffers minimum deviation of 38° while passing through a prism of refracting angle 60°. Refractive index of the prism material is take sin 49 ∘ = 0 .7547
Which of the prism is used to see infrared spectrum of light
When white light enters a prism, it gets split into its constituent colours. This is due to
For a prism of refractive index 1.732, the angle of minimum deviation is equal to the angle of the prism. The angle of the prism is
For a normal eye, the least distance of distinct vision is
Astigmatism (for a human eye) can be removed by using
For the myopic eye, the defect is cured by
Image formed on the retina is
If there had been one eye of the man, then
A person cannot see distinctly at the distance less than one metre. Calculate the power of the lens that he should use to read a book at a distance of 25 cm
How should people wearing spectacles work with a microscope
A man who cannot see clearly beyond 5 m wants to see stars clearly. He should use a lens of focal length
A man can see only between 75 cm and 200 cm. The power of lens to correct the near point will be
A man can see the objects upto a distance of one metre from his eyes. For correcting his eye sight so that he can see an object at infinity, he requires a lens whose power is or A man can see upto 100 cm of the distant object. The power of the lens required to see far objects will be
The far point of a myopia eye is at 40 cm. For removing this defect, the power of lens required will be
A man suffering from myopia can read a book placed at 10 cm distance. For reading the book at a distance of 60 cm with relaxed vision, focal length of the lens required will be
If the distance of the far point for a myopia patient is doubled, the focal length of the lens required to cure it will become
The sensation of vision in the retina is carried to the brain by
A man is suffering from colour blindness for green colour. To remove this defect, he should use goggles of
A short sighted person can see distinctly only those objects which lie between 10 cm and 100 cm from him. The power of the spectacle lens required to see a distant object is
When the power of eye lens increases, the defect of vision is produced. The defect is known as
A person wears glasses of power – 2.5 D. The defect of the eye and the far point of the person without the glasses are respectively
A person’s near point is 50 cm and his far point is 3 m. Power of the lenses he requires for (i) reading and (ii) for seeing distant stars are
A person cannot see objects clearly beyond 2.0 m. The power of lens required to correct his vision will be
A person wears glasses of power – 2.0 D. The defect of the eye and the far point of the person without the glasses will be
An eye specialist prescribes spectacles having a combination of convex lens of focal length 40 cm in contact with a concave lens of focal length 25 cm. The power of this lens combination in diopters is
Near and far points of a human eye are
Retina of eye acts like …….. of camera
Amount of light entering into the camera depends upon
A person uses spectacles of power +2D. He is suffering from
To remove myopia (short sightedness) a lens of power 0.66 D is required. The distant point of the eye is approximately
A person suffering from ‘presbyopia’ (myopia and hyper metropia both defects) should use
A man can see clearly up to 3 metres. Prescribe a lens for his spectacles so that he can see clearly up to 12 metres.
A satisfactory photographic print is obtained when the exposure time is 10 sec at a distance of 2 m from a 60 cd lamp. The time of exposure required for the same quality print at a distance of 4 m from a 120 cd lamp is
A person can not see the objects clearly placed at a distance more than 40 cm. He is advised to use a lens of power
A person uses a lens of power + 3D to normalise vision. Near point of hypermetropic eye is
A student can distinctly see the object upto a distance 15 cm. He wants to see the black board at a distance of 3 m. Focal length and power of lens used respectively will be
The light gathering power of a camera lens depends on
A camera objective has an aperture diameter d. If the aperture is reduced to diameter d 2 the exposure time under identical conditions of light should be made
In a compound microscope magnification will be large, if the focal length of the eye piece is
The magnifying power of a simple microscope can be increased, if we use eye-piece of
The maximum magnification that can be obtained with a convex lens of focal length 2.5 cm is (the least distance of distinct vision is 25 cm)
The power of two convex lenses A and B are 8 diopters and 4 diopters respectively. If they are to be used as a simple microscope, the magnification of
In order to increase the magnifying power of a compound microscope
If the focal length of the objective lens is increased then
The magnification produced by the objective lens and the eye lens of a compound microscope are 25 and 6 respectively. The magnifying power of this microscope is
The focal lengths of the objective and the eye-piece of a compound microscope are 2.0 cm and 3.0 cm respectively. The distance between the objective and the eye-piece is 15.0 cm. The final image formed by the eye-piece is at infinity. The two lenses are thin. The distances in cm of the object and the image produced by the objective measured from the objective lens are respectively
The objective lens of a compound microscope produces magnification of 10. In order to get an overall magnification of 100 when image is formed at 25 cm from the eye, the focal length of the eye lens should be
Least distance of distinct vision is 25 cm. Magnifying power of simple microscope of focal length 5 cm is
In a compound microscope cross-wires are fixed at the point
In a compound microscope, the focal lengths of two lenses are 1.5 cm and 6.25 cm an object is placed at 2 cm form objective and the final image is formed at 25 cm from eye lens. The distance between the two lenses is
The length of the tube of a microscope is 10 cm. The focal lengths of the objective and eye lenses are 0.5 cm and 1.0 cm. The magnifying power of the microscope is about
The magnifying power of a simple microscope is 6. The focal length of its lens in metres will be, if least distance of distinct vision is 25 cm
The angular magnification of a simple microscope can be increased by increasing
A compound microscope has two lenses. The magnifying power of one is 5 and the combined magnifying power is 100. The magnifying power of the other lens is
The image formed by an objective of a compound microscope is
An achromatic telescope objective is to be made by combining the lenses of flint and crown glasses. This proper choice is
The magnifying power of a telescope can be increased by
An observer looks at a tree of height 15 m with a telescope of magnifying power 10. To him, the tree appears
For observing a cricket match, a binocular is preferred to a terrestrial telescope because
To increase the magnifying power of telescope (f o = focal length of the objective and f e = focal length of the eye lens)
The focal length of the objective of a terrestrial telescope is 80 cm and it is adjusted for parallel rays, then its magnifying power is 20. If the focal length of erecting lens is 20 cm, then full length of telescope will be
In an astronomical telescope, the focal lengths of two lenses are 180 cm and 6 cm respectively. In normal adjustment, the magnifying power will be
In Gallilean telescope, if the powers of an objective and eye lens are respectively +1.25 D and – 20 D, then for relaxed vision, the length and magnification will be
The magnifying power of an astronomical telescope for relaxed vision is 16. On adjusting, the distance between the objective and eye lens is 34 cm. Then the focal length of objective and eye lens will be respectively
The aperture of a telescope is made large, because
When a telescope is adjusted for parallel light, the distance of the objective from the eye piece is found to be 80 cm. The magnifying power of the telescope is 19. The focal lengths of the lenses are
Two convex lenses of focal lengths 0.3 m and 0.05 m are used to make a telescope. The distance kept between the two is
All of the following statements are correct except
The length of an astronomical telescope for normal vision (relaxed eye) (f o = focal length of objective lens and f e = focal length of eye lens) is
The focal lengths of the objective and eye lenses of a telescope are respectively 200 cm and 5 cm. The maximum magnifying power of the telescope will be
The astronomical telescope consists of objective and eye-piece. The focal length of the objective is
Four convergent lenses have focal lengths 100 cm, 10 cm, 4 cm and 0.3 cm. For a telescope with maximum possible magnification, we choose the lenses of focal length
The focal length of objective and eye-piece of a telescope are 100 cm and 5 cm respectively. Final image is formed at least distance of distinct vision. The magnification of telescope is
If tube length of astronomical telescope is 105 cm and magnifying power is 20 for normal setting then calculate the focal length of objective.
The number of lenses in a terrestrial telescope is
An astronomical telescope of ten-fold angular magnification has a length of 44 cm. The focal length of the objective is
The focal lengths of the lenses of an astronomical telescope are 50 cm and 5 cm. The length of the telescope when the image is formed at the least distance of distinct vision is
The focal lengths of the objective and eye-piece of a telescope are respectively 100 cm and 2 cm. The moon subtends an angle of 0.5° at the eye. If it is looked through the telescope, the angle subtended by the moon’s image will be
The sun’s diameter is 1 .4 × 10 9 m and its distance from the earth is 10 11 m . The diameter of its image, formed by a convex lens of focal length 2m will be
An astronomical telescope has a magnifying power 10. The focal length of eyepiece is 20 cm. The focal length of objective is
In a simple microscope, if the final image is located at infinity then its magnifying power is
A simple magnifying lens is used in such a way that an image is formed at 25 cm away from the eye. In order to have 10 times magnification, the focal length of the lens should be
In a compound microscope the objective of f o and eyepiece of f e are placed at distance L such that L equals
An astronomical telescope has objective and eye-piece lens of powers 0.5 D and 20 D respectively, its magnifying power will be
A telescope has an objective lens of focal length 200 cm and an eye piece with focal length 2 cm. If this telescope is used to see a 50 meter tall building at a distance of 2 km, what is the height of the image of the building formed by the objective lens
A compound microscope has an eye piece of focal length 10 cm and an objective of focal length 4 cm. Calculate the magnification, if an object is kept at a distance of 5 cm from the objective so that final image is formed at the least distance vision (20 cm)
