A ray of monochromatic light is incident on an equilateral prism made of a material of refractive index 2 . The ray undergoes refraction such that the light ray inside the prism travels parallel to its base. The angle of deviation of the ray is :

Step-by-step solution

For an equilateral prism, the angle of the prism is A = 60^ . The refracted ray inside the prism is parallel to its base, which indicates that the prism is in the position of minimum deviation. In this position, the angle of refraction is r = A 2 = 60^ 2 = 30^ . Applying Snell's law at the first refracting surface: = i r 2 = i 30^ i = 2 1 2 = 1 2 This gives the angle of incidence i = 45^ . The angle of deviation in the position of minimum deviation is given by: = 2i - A = 2(45^ ) - 60^ = 90^ - 60^ = 30^ . Answer: 3