Question

The following figure shows the multiple reflections of a light ray along a glass corridor where the walls are either parallel or perpendicular to one another. If the angle of incidence at point $P$ is $30^\circ $ , then the angles of reflection of the light ray at points $Q$ , $R$ , $S$ and $T$ respectively are

• A. $30^\circ , \, 30^\circ , \, 30^\circ , \, 30^\circ $
• B. $30^\circ , \, 60^\circ , \, 30^\circ , \, 60^\circ $
• C. $30^\circ , \, 60^\circ , \, 60^\circ , \, 30^\circ $
• D. $60^\circ , \, 60^\circ , \, 60^\circ , \, 60^\circ $

Answer 1

Answer: (C)

According to the law of reflection on a plane mirror, the incident angle is equal to the reflection angle.
i.e., $\angle i=\angle r$
Using this rule and the properties of a right angle triangle, we obtain:

So, the angles of reflection of light at points $Q,R,S,T$ are $30^\circ , \, 60^\circ , \, 60^\circ , \, 30^\circ $ respectively.