Question

When a plane mirror is rotated through an $\theta$ the reflected ray turns through angle $2\theta$ then the angle of deviation is :

• A. $180-2(i-\theta )$
• B. $90-2(i-\theta )$
• C. $180-2(i+\theta )$
• D. $90+2(i-\theta )$

Answer 1

The correct option is C $180-2(i+\theta )$

When mirror is rotated by $\theta$

Incidence angle = $i+\theta$

$\delta ={180}^0-2$ (Incidence angle)

$={180}^0-2(i+\theta )$