Q. $P$ is a point on the axis of a convex mirror. The image of $P$ formed by the mirror, coincides with $P$. A rectangular glass slab of thickness $t$ and refractive index $\mu$ is now introduced between $P$ and the mirror. For the image of $P$ to coincide with $P$ again, the mirror must be moves
A) Towards $P\ $by $(\mu - 1)t$
B) Away from $P\ $by $(\mu - 1)t$
C) Towards $P$ by $t\left( 1 - \frac{1}{\mu} \right)$
D) Away from $P$ by $t\left( 1 - \frac{1}{\mu} \right)$
Explanation
(c) When a slab of thickness $t$ is introduced between $P$ and the mirror, the appearent position of $P$ shifts towards the mirror by $\left( t - \frac{t}{\mu} \right).\ $Hence,$\ $the mirror must be moved in the same direction through the same distance
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.