Light is incident from glass (μ = 1.5) to air. Sketch the variation of the angle of deviation δ with the angle of incident i for 0<i<90°.

Refractive index of glass is

Refractive index of air is

Angle if incidence = i


Critical Angle=


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.