Question

Refraction takes place at a concave spherical boundary separating glass and air medium. The refractive index of the glass is 3/2 . The radius of curvature of the refracting surface is R. For the image to be real the object distance should be greater than IR, where I is an integer. Find the minimum value of I. 

Answer 1

1/v - 3/2u = -1/2R

For image to be real, V > 

3/2u - 1/2R > 0

3/2u - 1/2R > 0

3/24 1/2R

U < 3R 

So minimum value  → 3R

Hence I = 3