Question

A student very cautiously traces the path of a ray through a glass slab for different values of the angle of incidence (∠i). He then measures the corresponding values of the angle of refraction (∠r) and the angle of emergence (∠e) for every value of the angle of incidence. On analysing these measurements of angles, his conclusion would be

(A) ∠i > ∠r  > ∠e

(B) ∠i = ∠e  > ∠r

(C) ∠i < ∠r  < ∠e

(D) ∠i = ∠e  < ∠r

Answer 1

Since the emergent ray is always parallel to the incident ray, therefore the angle of incidence is always equal to the angle of emergence i.e.

∠i = ∠e   ..... (i)

Also, when a light ray travels from rarer to denser medium, it bends towards the normal. Hence

∠i > ∠r   ..... (ii)

From (i) and (ii), we get 

 ∠i = ∠e  > ∠r

Hence, the correct answer is ∠i = ∠e  > ∠r