Question

A biconvex lens made of glass (refractive index 1.5) has two spherical surfaces having radii 20 cm and 30 cm. Calculate its focal length.

Answer 1

`1/f = (mu - 1) (1/R_1 + 1/R_2)`

`1/f = (1.5 - 1) (1/30 + 1/20)`

f = 24 cm