CBSE Class 12 Physics 2024-25: Unit 8 Optics Competency-Based Questions with Answers; Download Free PDF

As the CBSE Class 12 board exams get closer, it’s important for students to understand the new exam pattern. Starting in the 2024-25 school year, CBSE will include 50% more competency-based questions. These questions will be both multiple choice and written, focusing on how to use what students have learned in real-life situations.

For Class 12 Physics, Unit - 8 on Optics, CBSE has provided competency-based questions that help improve understanding and application skills. It highlights key competency-based questions and provides answers to help students succeed. These questions are designed to help students strengthen their understanding and apply concepts effectively for their exams.

By practicing these competency-based questions, students will get familiar with the types of questions they are likely to face in the exam. The free PDF includes a variety of questions, such as multiple-choice (MCQs) and free-response questions, with answers provided to guide students in their preparation.

CBSE Class 12 Physics Chapter 8 Optics Important Competency-Based Questions

Q.1 An object is moved towards a concave mirror at a constant speed, from infinity to its focus. Which of the following statements correctly describe the corresponding motion in the image formed by the concave mirror?

A. The image moves slower initially and faster later on, away from the mirror.
B. The image moves faster initially and slower later on, towards the mirror.
C. The image moves at a constant speed, faster than the object, away from the mirror.
D. The image moves at a constant speed, slower than the object, towards the mirror.

Answer. A. The image moves slower initially and faster later on, away from the mirror.

Q.2 An incident light ray falls on a glass prism at an angle of 60o and emerges with an angle of 30o with its initial incident direction. If the angle of the prism is 30o, then which of the following is an INCORRECT statement?

A. Refractive index of the prism is √3.
B. The light undergoes minimum deviation through the prism (i.e., r₁ = r₂).
C. The emergent ray is perpendicular to the face from which it emerges.
D. Angle of refraction r1 at the incident face is same as angle of the prism.

Answer. B. The light undergoes minimum deviation through the prism (i.e., r₁ = r₂).

Q.3 Which of the following actions will lead to an increase in the magnifying power of an astronomical telescope?

A. Increase in the length of the telescope tube.
B. Interchange the objective and the eyepiece of the telescope.
C. A small piece of paper on the objective of the telescope pointed towards the moon.
D. Increase in the focal length of the objective and decrease in the focal length of the eye piece.

Answer. D. Increase in the focal length of the objective and decrease in the focal length of the eye piece.

Q.4 In a glass prism of refractive index n, identify the condition for which an incident light emerges out of the prism with a non‐zero deviation.

A. Angle of prism is zero
B. Angle of incidence is equal to angle of emergence
C. The n of the material of the prism is same as its surroundings
D. Sum of angle of incidence and angle of emergence is equal to angle of prism

Answer. B. Angle of incidence is equal to angle of emergence

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Q.5 Two superimposing waves are of amplitudes a1 and a2 and intensities are I₁ and I₂ respectively. If the ratio I₁:I₂ is 1:16, what will be the ratio of their maximum to minimum intensities upon super‐imposition?

A. 1/4
B. 4/1
C. 25/9
D. 9/25

Answer. C. 25/9

Q.6 A 5% change in wavelength is observed in the light received from a distant star. What is the speed of the moving star?

A. c
B. 0.05 c
C. 20.0 c
D. 0.02 c

Answer. B. 0.05 c

Q.7 Loud music being played on the TV in the adjacent room can be heard through the slightly open door of your study room. But you cannot see what is happening outside your room. Why is it that you can hear the sounds but unable to see through the narrow opening of the door?

A. Sound waves can pass right through the walls, but light waves cannot.
B. The open door is a small slit for sound waves, but a large slit for light waves.
C. Light waves diffract efficiently through the single slit of the open doorway, but sound waves cannot.
D. Light waves can travel only along straight lines whereas sound waves can travel along curved paths.

Answer. B. The open door is a small slit for sound waves, but a large slit for light waves.

Q.8 An object is placed on the optical bench at a distance of 40 cm from the convex mirror of focal length 10 cm. A plane mirror is placed in between the object and the convex mirror such that it covers the lower half of the convex mirror.

Find the distance from the object where the plane mirror be placed, so that no parallax is observed between the two images formed by the two mirrors.

Answer. Using mirror formula for the convex mirror, 1/f = 1/v + 1/u 1/10 = 1/v + 1/(‐40)

Solving for v, v = 8 cm

👉 CBSE Class 12 Study Materials

CBSE Class 12 Syllabus 2024-25	CBSE Class 12 Previous Year Papers
NCERT Books For Class 12 Books	NCERT Class 12 Solutions
CBSE Class 12 Full Study Material	CBSE Class 12 Sample Paper 2024-25