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. $\theta \geq 120^{\circ}$
• B. $\theta \geq 90^{\circ}$
• C. $\theta \leq 120^{\circ}$
• 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 $n \leq 2$
$n-1 \leq 2$
$n \leq 3$
$\frac{360^{\circ}}{\theta} \leq 3$
$120 \leq \theta$
$\theta \geq 120^{\circ}$