Question

On a plane mirror a ray of light is incident at an angle of ${60}^{\circ }$ To make reflected ray vertical, at what angle with vertical must a plane mirror be placed?

Answer 1

Angle difference between incident and vertical direction is $\theta ={60}^o$

When mirror is tilted, $i+r={60}^o$

$2i={60}^o$ $\because i=r$

$i={30}^o$

Hence, tilted angle of mirror is ${30}^o$ anticlockwise.