A concavo-convex lens is made of glass of refractive index `1.5.` The radii of curvature of its two surfaces are `30 cm` and `50 cm.` Its focal length when placed in a liquid of refractive index `1.4` is

A plano-convex lens is made of glass of refractive index 1.6. the radius of curvature of its curved surface is 30 cm. What is the focal length of the lens ?

A plano convex lens is made of glass of refractive index 1.5. The radius of curvature of its convex surface is R. Its focal length is

A plano convex lens is made of glass of refractive index 1.5. The radius of curvature of its convex surface is R. Its focal length is

A concavo-convex lens has refractive index 1.5 and the radii of curvature of its surfaces are 10 cm and 20 cm. The concave surface is upwords and is filled with oil of refractive index 1.6. The focal length of the combination will be

A concavo-convex lens has refractive index 1.5 and the radii of curvature of its surfaces are 10 cm and 20 cm. The concave surface is upwords and is filled with oil of refractive index 1.6. The focal length of the combination will be

A double convex thin lens made of glass of refractive index 1.6 has radii of curvature 15 cm each. The focal length of this lens when immersed in a liquid of refractive index 1.63 is :