Q20 of 22 Page 157

A light ray falls on one of the faces of a prism at an angle 40o so that it suffers angle of minimum deviation of 30°. Find the angle of prism and angle of refraction at the given surface.

Given: Angle of incidence, i = 40o


Angle of minimum deviation, D = 30o


Let angle of prism be A


Using formula: A+D = 2i


A = 2i-D =2(40o)-30o = 80o – 30o = 50o


A = 50o


Using formula: r = A/2 (when angle of minimum deviation is considered)


r = 50o/2 = 25o


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