Refraction takes place at a concave spherical boundary separating glass air medium. For image to be real the object distance $(\mu g=\large\frac{3}{2})$

Question

(a) Should be greater than 3 times the radius of curvature of refracting surface.

(b)Should be greater than 2 times the radius of curvature of refracting surface.

(c) Should be greater than radius of curvature of refracting surface.

(d)Is independent of radius of curvature of refracting surface