Draw a ray diagram showing the formation of the image by a point object on the principal axis of a spherical convex surface separating two media of refractive indices `n_1 and n_2`, when a point source is kept in rarer medium of refractive index `n_1`. Derive the relation between object and image distance in terms of refractive index of the medium and radius of curvature of the surface. Hence, obtain the expression for lens maker's formula in the case of thin convex lens.