The radii of curvature of the two surfaces of a lens are 20 cm and 30 cm and the refractive index of the material of the lens is 1.5. If the lens is concave -convex, then the focal length of the lens is

The radii of curvature of the two surface of a lens are 20 cm and 30 cm and the refractive index of the material of the lens is 1.5 . If the lens is concave - convex, then the focal length of the lens is :

The radii of curvature of the two surfaces of a lens are 20cm and 30 cm and the refractive index of the material of the lens is 1.5 . If the lens is concave - convex, then the focal length of lens is

The radius of curvature of the curved surface of a plano-convex lens is 20 cm . If the refractive index of the material of the lens be 1.5 , it will

The radius of curvature of the curved surface of a plano-convex lens is 20 cm . If the refractive index of the material of the lens be 1.5 , it will

The radius of curvature of the curved surface of a plano-convex lens is 20 cm. If the refractive index of the material of the lens be 1.5, it will