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 ?

Explanation

According to lens-maker.s formula,
` (1)/(f) = (mu-1) [(1)/(R_1) -(1)/(R_2)]`
Here f=30 cm ,`R_1 = 10 cm and R_2 = oo`
so ` (1)/(30) = (mu-1) [(1)/(10) - (1)/(oo)]`
` i.e., 3 mu -3=1 or mu =(4 //3)`