Question

A ray of light is incident on a 60${}^o$ prism at the minimum deviation position. The angle of refraction at the first face (i.e., incident face) of the prism is :

• A. zero
• B. 30${}^o$
• C. 45${}^o$
• D. 60${}^o$

Answer 1

The correct option is B 30${}^o$

Angle of prism, $A=r_1+r_2$

For minimum deviation

$r_1=r_2=r$ $\therefore$ $A=2r$

Given, A = 60${}^o$

Hence, $r=\frac{A}{2}=\frac{{60}^o}{2}={30}^o$