Discussion Forum



1)

A ray of light is incident on a plane mirror at an angle of 30°. At what angle with the horizontal must plane mirror be placed so that the reflected ray becomes vertically upwards?


A) $40^{0}$

B) $20^{0}$

C) $30^{0}$

D) $60^{0}$

Answer:

Option C

Explanation:

 When a light ray falls on a mirror at an angle 30°, then the reflected ray will make the same angle with the plane as shown in fig(i) 2352021629_p5.JPG

 In order to make the reflected ray vertical, the mirror should be rotated at an angle of 60°.

 So, the mirror should be  tilted by  $\frac{60^{0}}{2}=30^{0}$  Fig (ii)