Q: A 60° prism has a refractive index of 1.5 .Calculate (a)the angle of incidence for minimum deviation, (b) the angle of emergence of light at maximum deviation.

Sol: (a) As the prism is in the position of minimum of deviation,

r = (A/2 )=(60°/2)= 30°, so that at either face sin i = 1.5 sin30° = 0.75 or i = sin^{-1} (0.75) = 49°