BlogNCERTPhysics Important Topic: Optical Instruments

Physics Important Topic: Optical Instruments


Optics is the study of light that can be seen with the naked eye. We also investigate how optics may be used to improve human eyesight and conduct other activities in optics. We can say that optical instruments are equipment that use mirrors and lenses to reflect and refract light in order to create images. The light understanding was essential for the development of optical instruments. Telescopes, microscopes, cameras, and other optical devices are examples. The equipment that processes photons to enhance images for viewing/analyzing their features is known as optics and optical instruments. The eyes are a natural optical tool, similar to a camera, that allows us to do so.

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    The information about Optics and optical instruments from various physics-related articles are available here. Optical instruments and their general concepts are important topics in physics. Students who want to flourish in physics need to be well known about optical instruments to get deep knowledge about it to do well on their exams. The definitions, uses, and principles are provided here to assist students in effectively understanding the respective topic. Continue to visit our website for additional physics help.


    Optical instruments are devices that process light waves in order to improve the clarity of an image. Optical equipment, such as a magnifying lens or a more advanced device like a microscope or telescope, enlarge objects and allow us to see them in more detail. Converging lenses make things appear larger, but diverging lenses invariably result in smaller images.

    When using a converging lens, keep in mind that if an object is at a greater distance, the picture will be reduced and will be much closer to the focal point. The image goes beyond the focal point and enlarges as the object continues to move in the direction of the lens. The picture and the object are the same sizes when the item is placed at 2F, which is two times the focal distance from the lens. When an object moves from 2F to F, the image of the object continues to move out of the lens and enlarges until it reaches infinity when the object reaches F. The picture moves in the direction of the lens from negative infinity as the object goes closer to the lens, and it grows smaller as the object gets closer to the lens.

    Now, we can look into various optical instruments:

    (1) The Eye

    The human eye is a complicated optical device that allows us to see all of the objects around us. Let’s have a look at the human eye’s structure. Sclera is the white protective membrane that can be seen when looking directly into the eye. The outer layer of the eyeball is thick, opaque, and fibrous.

    The Iris is the round component. The colour of the iris determines the appearance of the eye. The Pupil is the translucent spot in the center of the iris. The iris functions similarly to a camera’s shutter. It collects the majority of the light that falls on it before allowing it to enter through the pupil. When light falls on the eyes, the iris controls how much light enters the eye; it extends when the light is dark all around and shrinks when the light is bright.

    The size of the pupil determines how much light enters the inner region of the eye. In strong light, the iris compresses the pupil, limiting the amount of light that enters the eye, whereas, in low light, it widens the pupil, allowing more light to enter. The form of the eyeball is spherical. Because of the presence of rods and cones, the retina of the eye is capable of detecting light and colour.

    The cornea is the first refractor of light entering the human eye. The iris is then struck by the refracted light. The lens is located just behind the iris, and light refracted via the pupil falls on it, forming a sharp image. We can see the thing clearly because the image is formed precisely on the retina.

    (2) Lenses

    An eye’s near vision is 25 cm on average. If a person’s near point is less than 25 cm, he can easily perceive local items but has trouble detecting far-off objects. Concave lenses are used in this scenario to focus far-off divergent light rays onto the retina.

    When the close point is more than 25 cm away, however, this person can see far-off items but has trouble watching adjacent ones.

    When an image is brought very close to the eye, the eyes are unable to converge the light rays at the retina; instead, they converge outside the retina, resulting in a fuzzy image. Convex lenses are used to converge and focus the light rays on the retina in this way.

    (3) Magnifying Glass

    A magnifying glass is a converging lens that enlarges an object by creating a virtual image of it. If we position a little item, such as a tree, in front of the lens’ focus point (far from the near point), the lens diverges these rays and creates a virtual image of the tree, which enlarges it.

    Depending on how much angle an object is subtended, every object requires some level of light vision. When you draw the tree closer to your eye, though, the image blurs. So, if we want to look at objects that are really far away, such as stars, planets, and so on, we’ll need an astronomical telescope.

    (4) The Microscope

    Microscopes, as we all know, are optical instruments that are used to view minute objects. A basic microscope is an optical instrument that humans use to magnify small objects in order to see them clearly. It has a short focal length and is a convex lens. For magnification, this microscope is placed at a close distance from the object, resulting in a virtual image. We can see very little letters and patterns with a basic microscope. These are also used by watchmakers.

    With a compound microscope, we can achieve extremely high magnification levels. This microscope is used to examine microscopic objects such as bacteria. It is made up of two convex lenses, with magnification in both of them. Eyepiece, objective lens, fine and coarse adjustment screws are the components of a compound microscope.

    (5) Telescope

    Telescopes are instruments that expand images of far-away objects that appear very small due to their distance, such as distant stars. Convex lenses are the sort of lenses used in telescopes to magnify images. Reflecting and refracting telescopes are the two types of telescopes. Refracting telescopes utilize a convex lens to capture and focus light while reflecting telescopes employ a concave mirror. Convex lenses are employed in the eyepieces of both telescopes to expand the view.

    (6) Periscope

    A periscope allows us to see the world from one corner of our room via video streaming from our smartphone or laptop. It’s an optical apparatus that uses prisms, lenses, and mirrors to reflect pictures via a tube, which is known as the Periscope tube. When light from a distant source strikes the top mirror, it is reflected at a 90° angle down the tube.

    (7) Camera

    A camera is an optical tool that aids in the production of an image as well as recording it. The image may be detected by electronic sensors and stored digitally, or it could be recorded on film. The aperture in a camera is the opening through which light passes and enters the camera. The development of a diminished actual image occurs when light passes through the lens. It’s likely that the camera’s lens will shift back and forth in order to bring the image into focus. The shutter controls the quantity of light that reaches the sensors, and it stays open for longer in weak light to allow more light in.

    (8) Optical Fibres

    Sound or images are encoded in the pulses of laser beams, which are conveyed across optical fibres. Because all of the light is reflected off of the interior of the fibre, there is no way for it to escape. As a result, the light signals remain bright even at extended distances. A single signal does not have to flow through an optical fibre at the same moment. Fibers are employed in a variety of applications in real life, including cable TV, telephone, and Internet signals, among others.

    Also read: Important Topic of Physics: Wave Optics

    Frequently Asked Questions (FAQs)

    What is meant by the persistence of vision?

    When the image of the item is generated at the retina of the eye, the human eye continues to view the image for some time after the object is removed. The persistence of vision in the human eye is the name given to this ability. The image of an object lasts at least 1 / 16 of a second on the retina of the human eye. The notion of persistence of vision is most commonly used in cinematography, where movies are projected on a screen captured by a movie camera. The image is displayed at 24 frames per second rate.

    What is meant by short-sightedness?

    Short-sightedness, often known as myopia, is an eye disorder in which items at a distance begin to blur while objects closer to the eye are viewed clearly. It's a pretty frequent eye problem. Mild short-sightedness may not necessitate treatment. Short-sightedness can be avoided by not sitting in front of the television or any other screen for too long. Laser treatments, corrective lenses, and lens implants can all be used to cure short-sightedness.

    What are some of the similarities between lenses and mirrors?

    Both a convex lens and a concave mirror can have a positive focal length and produce identical pictures, as well as converge parallel rays to a focal point. Both a convex mirror and a concave lens can have a negative focal length, allowing only minuscule and virtual images to be formed, and both can divert parallel rays away from a focus point.

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