Question

point luminous object (O) is at a distance h from front face of a glass slab of width d and of refractive index p. On the back face of slab is a reflecting plane mirror. An observer sees the image of object in mirror as shown in figure. Distance of image from front face as seen by observer will be

• A. $h+\frac{2d}{\mu }$
• B. $2h+2d$
• C. $h+d$
• D. $h+\frac{d}{\mu }$

Answer 1

Answer: (A)

As shown in figure glass slab will form the image of bottom i.e.y mirror $M{M}^{\prime }$ at a depth $(\frac{d}{\mu })$ from its front face. So the distance of object $O$ from virtual mirror $m{m}^{\prime }$ will be $h+(\frac{d}{\mu })$.
Now as a plane mirror forms image behind the mirror at the same distance as the object is in front of it, the distance of image $I$ from mm will be $h+(\frac{d}{\mu })$ and as the distance of virtual mirror from the front face of slab is $(\frac{d}{\mu })$, the distance of image $I$ from front face as seen by
observer $=[h+\frac{d}{\mu }]+\frac{d}{\mu }$
$=h+\frac{2d}{\mu }$