Question

A ray of light is normally incident on one face of an equilateral glass prism. Will the light ray suffer minimum deviation by the prism ?

• A. True
• B. False

Answer 1

The correct option is B False

When the ray strikes normally, it doesn't undergo any deviation and strikes the base with an angle of incidence of ${60}^o$ which leads to total internal reflection at the base. Since the angle of reflected ray is ${60}^o$, it will strike the second face normally and does not undergo dispersion and an angle of deviation of ${90}^o$.