Question

The radius of curvature of the convex face of a plano convex lens is 12cm and the refractive index of the material of the lends 1.5. Then, the focal length of the lens is
A. 6cm
B. 12cm
C. 18cm
D. 24cm

Answer 1

Correct Answer - D
We know that, `(1)/(f)=(n-1)(1)/(R )`
Given, R=12cm and r=1.5
Here, `f=(R)/(n-1)=(12)/(1.5-1)=(12)/(0.5)=24cm`