Q. Two plane mirrors $A$ and $B$ are aligned parallel to each other, as shown in the figure. A light ray is incident at an angle of $30{^\circ}$ at a point just inside one end of $A$. The plane of incidence coincides with the plane of the figure. The maximum number of times the ray undergoes reflection (including the first one) before it emerges out is
A) 28
B) 30
C) 32
D) 34
Explanation
(b) From the following ray diagram
$d = 0.2\tan{30{^\circ}} = \frac{0.2}{\sqrt{3}}$
$\Rightarrow \frac{I}{d} = \frac{2\sqrt{3}}{0.2/\sqrt{3}} = 30$
Therefore maximum number of reflections are 30
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.