A ray of light is incident on a 75° prism at the position of minimum deviation. The angle of refract

Question

A ray of light is incident on a 75° prism at the position of minimum deviation. The angle of refraction at the first face (incident face) of the prism is

Professor PC Thomas Classes · Answer

(b) : For a prism, the angle of the prism is $A = r_1 + r_2$. In the position of minimum deviation, the ray passes symmetrically through the prism, meaning the angle of refraction at both faces is equal ($r_1 = r_2 = r$). Therefore, $A = 2r$. Given the angle of the prism $A = 75^\circ$, the angle of refraction at the first face is $r = A / 2 = 75^\circ / 2 = 37.5^\circ$.