Question

A very expensive diamond is polished into a perfect sphere of radius $5cm$. The back surface of the sphere is then covered with silver. If $d$ is the distance of the source of light $S$ from the surface of sphere, then the image coincides with the source. If the index of refraction of diamond is $2.4$, then $d=\dots \times 5cm$.

Answer 1

Answer: 5

Considering refraction at curved surface:

$\frac{2.4}{2\times 5}+\frac{1}{x}=\frac{2.4-1}{5}$
$x=25cm$