Ray Optics and Optical Instruments is one of the most important topics in Class 12 Physics. It helps students understand how light behaves when it interacts with mirrors, lenses, and other optical devices. This topic forms the foundation for many real-world applications, including cameras, telescopes, microscopes, and even our understanding of how the human eye works.
In ray optics, we study the properties of light using the concept of rays. A ray is a straight-line path along which light travels. This simple approach allows us to explain complex phenomena like reflection, refraction, and the formation of images. For example, when light hits a mirror, it reflects and creates an image, and when it passes through a lens, it bends and focuses. These basic principles are essential for understanding how optical instruments work.
Optical instruments, such as telescopes and microscopes, use the properties of lenses and mirrors to magnify objects or bring them into focus. These tools are crucial for scientists, engineers, and even doctors in their daily work. Whether it’s observing distant stars or diagnosing a medical condition, optical instruments rely on the laws of ray optics.
This collection of Multiple Choice Questions (MCQs) on Ray Optics and Optical Instruments is designed to help students master this topic in a clear and practical way. The MCQs cover all the key concepts, such as reflection, refraction, dispersion, total internal reflection, and image formation. They also include questions on the working principles of optical instruments like microscopes, telescopes, and periscopes.
Practicing these MCQs will help students strengthen their understanding of the subject and prepare effectively for their board exams, competitive exams like JEE and NEET, and school-level assessments. Each question comes with clear options and explanations to make learning easy and enjoyable.
By solving these questions, students can identify their strengths and focus on areas that need improvement. This will not only build confidence but also enhance problem-solving skills, which are essential for mastering Physics. So, dive into this collection of MCQs and explore the fascinating world of ray optics and optical instruments!
Class 12 Physics Ray Optics & Optical Imstruments MCQs
Ques 1. What happens when light enters a new medium?
(a) Both wavelength and frequency increase
(b) Wavelength increases, frequency remains unchanged
(c) Both wavelength and frequency decrease
(d) Wavelength decreases, frequency remains constant
Answer: (b) Wavelength increases, frequency remains unchanged
Explanation: When light travels from one medium to another, its speed changes. This causes the wavelength to increase or decrease, but the frequency of light remains constant.
Ques 2. Which type of light deviates the most when passing through a prism?
(a) Red light
(b) Violet light
(c) Neither (a) nor (b)
(d) Both (a) and (b)
Answer: (b) Violet light
Explanation: Violet light has a shorter wavelength and higher frequency compared to other colors, so it bends more sharply when passing through a prism.
Ques 3. Which property of light makes a mirage possible?
(a) Refraction
(b) Reflection
(c) Total internal reflection
(d) Diffraction
Answer: (c) Total internal reflection
Explanation: A mirage is caused by total internal reflection when light rays bend and reflect due to varying air densities near hot surfaces.
Ques 4. What is the key principle behind optical fibers?
(a) Refraction
(b) Diffraction
(c) Scattering
(d) Total internal reflection
Answer: (d) Total internal reflection
Explanation: Light is guided through optical fibers using total internal reflection, allowing it to travel long distances without significant loss.
Ques 5. What happens to the dispersive power of a prism when it is immersed in water?
(a) Increases
(b) Decreases
(c) Remains the same
(d) No effect
Answer: (b) Decreases
Explanation: When a prism is placed in water, the difference in refractive indices between the prism and the surrounding medium reduces, decreasing its dispersive power.
Do Check: NCERT Solutions for Class 12 Physics Chapter 9 Ray Optics and Optical Instruments
Ques 6. Which mirror provides the largest field of view?
(a) Concave mirror
(b) Convex mirror
(c) Plane mirror
(d) Cylindrical mirror
Answer: (b) Convex mirror
Explanation: A convex mirror diverges light, allowing it to cover a larger area, which is why it’s used for rearview mirrors.
Ques 7. Which of the following cannot be polarized?
(a) Radiowaves
(b) Transverse waves
(c) Sound waves
(d) X-rays
Answer: (c) Sound waves
Explanation: Sound waves are longitudinal and cannot be polarized because their oscillations occur in the same direction as their propagation.
Ques 8. What happens when a convex lens is placed in a liquid with the same refractive index?
(a) Focal length becomes zero
(b) Focal length becomes infinite
(c) Focal length decreases but remains finite
(d) No change in focal length
Answer: (b) Focal length becomes infinite
Explanation: When the refractive indices of the lens and the liquid are the same, the lens cannot bend light, effectively making its focal length infinite.
Ques 9. For a telescope, how does the diameter of the objective lens affect its performance?
(a) Resolving power increases with a larger diameter
(b) Magnifying power increases with a larger diameter
(c) Resolving power decreases with a larger diameter
(d) Magnifying power decreases with a larger diameter
Answer: (a) Resolving power increases with a larger diameter
Explanation: A larger objective lens gathers more light, improving the resolving power and allowing finer details to be observed.
Ques 10. What is the minimum angle between two plane mirrors to form three images?
(a) 30°
(b) 60°
(c) 90°
(d) 120°
Answer: (c) 90°
Explanation: At 90°, two mirrors produce three distinct images due to multiple reflections between them.
Do Check: Ray Optics and Optical Instruments Class 12 Notes Chapter 9
Ques 11. What type of image is formed by a plane mirror?
(a) Real, inverted, and of equal size
(b) Virtual, erect, and of equal size
(c) Real, erect, and magnified
(d) Virtual, inverted, and diminished
Answer: (b) Virtual, erect, and of equal size
Explanation: Plane mirrors form images that appear behind the mirror, are upright, and have the same size as the object.
Ques 12. A light ray strikes a mirror normally. What are the angles of incidence and reflection?
(a) 0°, 0°
(b) 90°, 0°
(c) 0°, 90°
(d) 90°, 90°
Answer: (a) 0°, 0°
Explanation: When light strikes a surface at 90° (normally), it reflects back on the same path, with no deviation.
Ques 13. If two plane mirrors are parallel, how many images are formed?
(a) 1
(b) 2
(c) 3
(d) Infinite
Answer: (d) Infinite
Explanation: Parallel mirrors cause endless reflections, creating an infinite series of images.
Ques 14. How does angular magnification of a simple microscope increase?
(a) By increasing lens power
(b) By increasing focal length
(c) By reducing lens aperture
(d) By enlarging the object size
Answer: (a) By increasing lens power
Explanation: A more powerful lens bends light rays more sharply, enhancing angular magnification.
Do Check: Ray Optics and Optical Instruments MCQs for NEET Physics
Ques 15. What is the law governing the ratio of sine of incidence angle to sine of refraction angle?
(a) Refractive index of first medium with respect to second
(b) Refractive index of second medium with respect to first
(c) Snell’s law constant
(d) None of these
Answer: (b) Refractive index of second medium with respect to first
Explanation: According to Snell’s law, this ratio is the refractive index of the second medium relative to the first.
Ques 16. A man runs towards a stationary mirror at 15 m/s. What is the speed of his image relative to the mirror?
(a) 7.5 m/s
(b) 15 m/s
(c) 30 m/s
(d) 45 m/s
Answer: (b) 15 m/s
Explanation: The image appears to move at the same speed as the object relative to the mirror.
