Light is incident

Refractive index of glass is

Refractive index of air is

Angle if incidence = i

Critical Angle=

So,

⇒

⇒

⇒

The angle of deviation due to refraction from glass to air increases as the angle of incidence increases from 0° to 40°48''. The angle of deviation due to total internal reflection further increases for 40°48'' to 45° and then it decreases, as shown in the above graph.