Question

An object is placed at distance of 10 cm in air from the front surface of a thick glass slab of thickness 6 cm whose back surface has been silvered and is placed in air. The image is formed at a distance of 14 cm from the polished surface. The refractive index of the material of the thick mirror is

• A. 1.2
• B. 1.3
• C. 1.4
• D. 1.5

Answer 1

The correct option is A 1.2

$AB=App.Depth=x=\frac{6}{\mu }$
Image will be formed at the same distance as the object.

Hence $(6-x)+14=10+x$
$\Rightarrow 10=2\times \frac{6}{\mu }$
$\Rightarrow \mu =\frac{12}{10}=1.2$