The radii of curvature of the surfaces of a double convex lens are `20 cm and 40 cm` respectively, and its focal length is `20 cm`. What is the refractive index of the material of the lens ?

The radii of curvature of the faces of a double convex lens are 10 cm and 12 cm respectively.If the focal length of the lens is 12 cm ,find the refractive index of the material of the lens.

The radii of curvature of the faces of a double convex lens are 20 cm and 20 cm. Its focal length is also 20 cm. What is the refractive index of the glass?

(i) If f = + 0.5 m , what is the power of the lens ? (ii) The radii of curvature of the faces of a double convex lens are 9 cm and 15 cm . Its focal length is 12 cm . What is the refractive index of glass ?

The radii of curvature of the faces of a double convex lens are 20 cm and 30 cm. Its focal length is 24 cm. What is the refractive index of the glass?

The radii of curvature of the faces of a double convex lens are 10 cm and 15 cm, Its focal length is 12 cm. What is the refractive index of the glass ?