Question

An electric spheres of radius R and refractive index n kept in air at what distance from the surface of the sphere should a point object be placed on the principal axis so as to form a real image at the same distance from the second surface of the sphere?

Answer 1

Answer:

For refraction from the spherical surface, u=−2R

Using

v

μ

2

−

u

μ

1

=

R

μ

2

−μ

1

This gives v=1.5R

Now this image acts as object for reflection from plane mirror, which gives image at the same place as object. And again a back refraction takes place to obtain image at the initial position