A ray of light is incident at an angle of incidence, i,

A ray of light is incident at an angle of incidence, i, on one face of prism of angle A (assumed to be small) and emerges normally from the opposite face. If the refractive index of the prism is µ, the angle of incidence i, is nearly equal to :

For normally emerge e = 0
Therefore r₂ = 0 and r₁ = A
Snell’s Law for Incident ray’s
1sin i = µ sin r₁ = µsin A
For small angle i = µA

	A
	2µ