What is the refractive index of material of a plano-convex lens , if the radius of curvature of the convex surface is 10 cm and focal length of the lens is 30 cm ?

Options

A. `6/5`
B. `7/4`
C. `2/3`
D. `4/3`

Answer

D

Explanation

According to lens maker's formula ltbr gt `1/f = (mu - 1) ((1)/(R_(1)) - (1)/(R_(2)))`
Here, `f = 30 cm, R_(1) = oo` , (For plane surface)
`R_(2) = -10 cm`
`:. 1/30 = (mu - 1) ((1)/(oo) - (1)/(-10)) , 1/30 = ((mu - 1))/(10)` or `mu = 4/3`