A thin plano convex lens made of glass of refractive index 1.5 is immersed in a liquid of refractive index 1.2. When the plane side of the lens is…

A thin plano convex lens made of glass of refractive index $\displaystyle 1.5$ is immersed in a liquid of refractive index $\displaystyle 1.2$ . When the plane side of the lens is silver coated for complete reflection, the lens immersed in the liquid behaves like a concave mirror of focal length $\displaystyle 0.2$ m . The radius of curvature of the curved surface of the lens is