Question

After tracing the path of a ray of light passing through a rectangular glass slab for four different values of the angle of incidence, a student reported his observations in tabular form as given below:

S.No	∠ i	∠ r	∠ e
I	30°	19°	29°
II	40°	28°	40°
III	50°	36°	50°
IV	60°	40°	59°

The best observation is

(A) I

(B) II

(C) III

(D) IV

Answer 1

Observation III will give the best result because

(i) it has the largest angle of incidence, due to which the lateral displacement between the incident ray and the emergent ray will be maximum.

(ii) for light rays passing through a glass slab, ∠i=∠e and ∠r<∠i.

Hence, the correct option is C.