Question

The diagram below shows a light source P embedded in a rectangular glass block ABCD of critical angle 42°. Complete the path of the ray PQ till it emerges out of the block. [Write necessary angles].

Answer 1

At A
Angle of incidence = 38° >(i_c) 
∴ TIR takes place
The ray is now incident on surface CD at B, hex angle of incidence = 42°
∴ Angle of refraction = 90°