Question

A transparent sphere of radius R and refractive index $\mu$ is kept in air. At what distance from the surface of the sphere should a point object be placed so as to form a real image at the same distance from the other side of the sphere?

• A. $\frac{R}{\mu }$
• B. $\mu R$
• C. $\frac{R}{\mu -1}$
• D. $\frac{R}{\mu +1}$

Answer 1

Answer: (C)

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

R is the radius of the sphere

u is the refractive index of medium

$\frac{u_2}{v}-\frac{u_1}{v}=\frac{u_2-u_1}{r}$

refraction of surface of sphere

$\frac{u}{\infty }+\frac{1}{x}=\frac{u-1}{R}$

$\frac{1}{x}=\frac{u-1}{R}$

$x=\frac{R}{u-1}$