Ray Optics And Wave Optics PYQs — 14 UPSC CSE Previous Year Questions

Question 1

Rainbow is produced when sunlight falls on drops of rain. Which of the following physical phenomena are responsible for this? Dispersion Refraction Internal reflection Select the correct answer using the codes given below.

Accepted Answer

D. 1, 2 and 3

Question 2

Consider the following phenomena: Size of the sun at dusk Colour of the sun at dawn Moon being visible at dawn Twinkle of stars in the sky Polestar being visible in the sky Which of the above are optical illusions?

Accepted Answer

C. 1, 2 and 4

Question 3

Consider the following statements:

If magenta and yellow coloured circles intersect, the intersected area will have red colour.
If cyan and magenta coloured circles intersect, the intersected area will have blue colour.

Which of the statements given above is/are correct?

Accepted Answer

C. Both 1 and 2

Question 4

Consider the following natural phenomena: Terrestrial heating Reflection of light Refraction of light Diffraction of light Due to which of these phenomena is a mirage formed?

Accepted Answer

C. 1 and 3

Question 5

Assertion (A): A stick is dipped in water in a slanting position. If observed sideways, the stick appears short and bent at the surface of water. Reason (R): A light coming from the stick undergoes scattering from water molecules giving the stick a short and bent appearance.

Accepted Answer

C. A is true but R is false

Question 6

When a CD (compact disc used in audio and video systems) is seen in sunlight, rainbow like colours are seen. This can be explained on the basis of the phenomenon of:

Accepted Answer

D. refraction, diffraction and transmission

Question 7

When light waves pass from air to glass, the variables affected are:

Accepted Answer

D. wavelength and velocity

Question 8

Assertion (A): In a motion picture, usually 24 frames are projected every second over the whole length of the film. Reason (R): An image formed on the retina of eye persists for about 0.1 s after the removal of stimulus.

Accepted Answer

A. Both A and R are true, and R is the correct explanation of A

Question 9

Assertion (A): Small glass beads fixed on traffic signals glow brightly when light falls upon them. Reason (R): Light is totally reflected when the angle of incidence exceeds a certain critical value and light travelling in a denser medium is reflected from a rarer medium.

Accepted Answer

A. Both A and R are true, and R is the correct explanation of A

Question 10

When a CD (Compact Disc used in audio and video systems) is seen in sunlight, rainbow like colours is seen. This can be explained on the basis of the phenomenon of

Accepted Answer

D. refraction, diffraction and transmission

Question 11

Consider the following statements:

If a person looks at a coin which is in a bucket of water, the coin will appear to be closer than it really is.
If a person under water looks at a coin above, the water surface, the coin will appear to be at a higher level than it really is.

Which of the above statements is/are correct?

Accepted Answer

A. 1 and 2

Question 12

Endoscopy, a technique used to explore the stomach or other inner parts of the body is based on the phenomenon of

Accepted Answer

A. total internal reflection

Question 13

When a mirror is rotated by an angle θ, the reflected ray will rotate by:

Accepted Answer

D. 2θ

Question 14

Total internal reflection can take place when light travels from:

Accepted Answer

A. diamond to glass