In a plano-convex lens the radius of curvature of the convex lens is 10 cm. If the plane side is polished, then the focal length will be (Refractive index=1.5)

Options

A. 1.5
B. 1.66
C. 1.33
D. 3

Answer

C

Explanation

(c ) we have, `1/f=(mu-1)(1/R_(1)-1/R_(2))`
`1/30=(mu-1)(1/10)`
The refractive index of the material of the lens
`mu=4/3=1.33`