Question

A transparent cylinder has its right half polished so as to act as a mirror. A paraxial light ray incident from left, that is parallel to the principal axis, exits parallel to the incident ray as shown. The refractive index $n$ of the material of the cylinder is

• A. $1.2$
• B. $1.5$
• C. $1.8$
• D. $2.0$

Answer 1

The correct option is D $2.0$

Given for the refracting surface,

$u=-infinity$ ; $R=+R$ ; $v=+2R$

$\frac{{\mu }_2}{v}-\frac{{\mu }_1}{u}=\frac{{\mu }_2-{\mu }_1}{R}$

$\frac{\mu }{2R}=\frac{\mu -1}{R}$

$\mu =2$

option $D$ is correct