Question

A source of light lies on the angle bisector of two plane mirrors inclined at angle $\theta$. The values of $\theta$, so that the light reflected from one mirror does not reach the other mirror will be

• A. $\theta \ge 120^{\circ }$
• B. $\theta \ge 90^{\circ }$
• C. $\theta \le 120^{\circ }$
• D. None of the above

Answer 1

Answer: (A)

For the given condition, no successive reflection takes place.
So, the number of images will be $n\le 2$
$n-1\le 2$
$n\le 3$
$\frac{360^{\circ }}{\theta }\le 3$
$120\le \theta$
$\theta \ge 120^{\circ }$