Question

A plano-concave lens is made of glass of refractive index 1.5 and the radius of curvature of its curved face is 100 cm. What is the power of the lens?
A. `+0.5D`
B. `-0.5D`
C. `-2D`
D. `+2D`

Answer 1

Correct Answer - B
(b) The refractive index is 1.5 and the rdius of curvature of the curved face is 100 cm =1m and of the plane side is `oo`, hence
`P=1/f=(mu-1)(1/R_(1)-1/R_(2))`
Power of the lend,P`=(1.5-1)(1/oo-1/1)=-0.5D`