A small point object is inside a glass surface as shown. Refraction takes place at concave spherical boundry separating glass air medium. For the image to be real the object distance u is (R-Radius of curvature of the surface , $\mu of glass =\large\frac{3}{2}$ )

Question

 

$(a)\;u=2R \\ (b)\;u < 3R \\ (c)\;u > 3R \\ (d)\;u < R$