The focal lengths of four convex lens P,Q, R and S are 20cm, 15 cm, 5 cm and 10 cm, respectively. The lens having greatest power is:

The focal lengths of a convex lens for red, yellow and violet rays are 100 cm, 98 cm and 96 cm respectively. Find the dispersive power of the material of the lens.

The focal lengths of a convex lens for red, yellow and violet rays are 100 cm, 98 cm and 96 cm respectively. Find the dispersive power of the material of the lens.

The focal length of a convex lens is 20 cm.What is the power?

The focal length of a convex lens is 20 cm. What is the power?

Calculate the focal length of a convex lens whose radii of curvature of two surfaces is 10cm and 15cm respectively and its refractive index is 1.5.

If the focal length of a double convex lens is 12 cm and radii of curvatures of faces are 10 cm and 15 cm respectively, what is the refractive index of the lens?

The focal length of a convex lens is 20 cm. What is its power?