# A parallel beam of light is incident from air at an angle a on the side PQ of a right angled

A parallel beam of light is incident from air at an angle a on the side PQ of a right angled triangular prism of refractive index n = √2 . Light undergoes total internal reflection in the prism at the face PR when ∝ has a minimum value of 45°. The angle q of the prism is :

(A) 15°

(B) 22.5°

(C) 30°

(D) 45°