1.6 is a refractive index of plano-convex lens, then the radius of curvature of the curved surface is 60 cm. The focal length of the lens is………….. cm
$ here , {1 \over f } = (1.6 -1) \left( {1 \over 60 } - {1 \over \infty} \right) = {1 \over 100} $ $ \therefore f = 100 cm $