Two identical concave mirrors each of focal length f are facing each other as shown in the schematic diagram. The focal length f is much larger than the size of the mirrors. A glass slab of thickness

Question

Two identical concave mirrors each of focal length $f$ are facing each other as shown in the schematic diagram. The focal length $f$ is much larger than the size of the mirrors. A glass slab of thickness $t$ and refractive index $n_{0}$ is kept equidistant from the mirrors and perpendicular to their common principal axis. A monochromatic point light source $S$ is embedded at the center of the slab on the principal axis, as shown in the schematic diagram. For the image to be formed on $S$ itself, which of the following distances between the two mirrors is/are correct:

Screenshot 2026-02-08 at 9.37.33 PM.png

Question diagram: Two identical concave mirrors each of focal length f are fac

Options:(select one or more)

Answer:

A, B

Solution:

$\frac{S - t}{2} + \frac{t}{2 n _{0}} = 2 f S + t (\frac{1}{n _{0}} - 1) = 4 f S = 4 f + (1 - \frac{1}{n _{0}}) t$ Also $\frac{S - t}{2} + \frac{t}{2 n _{0}} = f S = 2 f + (1 - \frac{1}{n _{0}}) t$

TestHub · Accepted Answer

​ 2 S − t ​ + 2 n 0 ​ t ​ = 2 f S + t ( n 0 ​ 1 ​ − 1 ) = 4 f S = 4 f + ( 1 − n 0 ​ 1 ​ ) t ​ Also ​ 2 S − t ​ + 2 n 0 ​ t ​ = f S = 2 f + ( 1 − n 0 ​ 1 ​ ) t ​

Physics - Geometrical Optics Question with Solution | TestHub

Options:(select one or more)

Doubts & Discussion