Question

A plane glass mirror of thickness $3cm$ of material of $\mu =3/2$ is silvered on the back surface. When a point object is placed $9cm$ from the front surface of the mirror, then the position of the brightest image from the front surface is

• A. $9cm$
• B. $11cm$
• C. $12cm$
• D. $13cm$

Answer 1

Answer: (D)

$13cm$

A thick glass mirror produces a number of images.

There is an apparent shift of actual silvered surface toward the unsilvered face.

Effective distance of the reflecting surface from unsilvered face $=\frac{d}{\mu }=\frac{3}{3/2}cm=2cm$

Distance of the point object from effective reflecting surface $=9cm+2cm=11cm$.

Distance of image from the point object $=11cm+11cm=22cm$

Distance of image from unsilvered face

$=(22-9)cm=13cm$.