Question

The refractive index of a parallel glass slab is 1.57. A light, from medium Y, is incident on the glass slab. If the angle of incidence is 37°, then the angle of emergence, when the light emerges back to medium Y, is ____

(a) 37°

(b) 45°

(c) 54°

(d) 60°

This question was addressed to me in class test.

Question is taken from Velocity of Light in section Optics of Engineering Physics II

Answer 1

Right option is (a) 37°

The best explanation: In the given case, the light is initially in medium Y. It strikes the glass slab at 37° and later emerges back at medium Y at a certain angle to the normal, called angle of emergence. Now, since the opposite sides of the glass slab are parallel, the incident ray should be parallel to the emergent ray. Hence, the angle of incidence should be equal to the angle of emergence.

Hence, the angle of emergence = 37°.