A light ray falls perpendicular to one of the faces of a glass prism of angle 60 and refractive index 1.5,

Find;

a) the angle of emergence.

b) the angle of deviation.

Answer:

The question implies that the angle of incidence is 0

The ray will enter without any deviation. Therefore, the angle of incidence at the second face inside the prism = 60 degree

(From A +90+ (90-r2)=180)

Since the critical angle for glass is less than this, the ray of light will undergo total internal reflection. So it reflects towards the base internally.