Question

A convex lens is made-up of two different material. How many image will it form when object is kept in front of it?

Answer 1

The lens is made up of two different material which will have two different refractive index. According to lens maker's formula the focal length is a function of refractive index given by
$\frac{1}{f}=(n_e-1)(\frac{1}{R_1}-\frac{1}{R_2}$ )
This means that two different refractive indices will give two different focal length. Hence two different images will be formed corresponding to each lens halves.