Question

A light ray falls on a mirror and deviates by ${30}^{\circ }$, then the angle of incidence will be:

• A. ${75}^{\circ }$
• B. ${60}^{\circ }$
• C. ${90}^{\circ }$
• D. ${180}^{\circ }$

Answer 1

Answer: (A)

${75}^{\circ }$

Angle of deviation, $\theta ={30}^0$

Let the angle of incidence be $i$

$\therefore$ $\theta ={180}^0-2i$

or, $2i={180}^0-{30}^0={150}^0$

or, $i={75}^0$

So, the angle of incidence is ${75}^0$.