A convex lens of focal length 50 cm, a concave lens of focal length 50 cm and a concave lens focal lens 20 cm are placed in contact. The power of this combination in diopters will be

A convex lens of focal length 40 cm a concave lens of focal length 40 and a concave lens of focal length 15 cm are placed in contact. The power of this combination of are placed in contact. The power of this combination in diopters is

A convex lens of focal lenth 30 cm and a concave lens of focal length 60 cm are placed in contact.Find the power of the combination.

A convex lens of focal length 30 cm and a concave lens of focal length 0.6m are placed in contact. Find the power of the combination.

A convex lens of focal length A and a concave lens of focal length B are placed in contact. The focal length of the combination is

A convex lens of focal length A and a concave lens of focal length B are placed in contact. The focal length of the combination is

A convex lens of focal length x and a concave lens of focal length y are placed in contact. The focal length of the combination is

A convex lens of focal length 80 cm and a concave lens of focal length 50cm are placed in contact. The resulting will be—

A convex lens of focal length 25 cm and a concave lens of focal length 10 cm are joined together. The power of the combination will be

The power of a concave lens of focal length 50 cm is :