A`20cm` convex lens is placed in contact with a diverting lens of unknown focal length ,The lens combination acts as a converging lens and has a length of`30cm`.What is the focal length of the diverging lens.

A concave lens is kept in contact with a convex lens of focal length 20 cm . The combination works as a converging lens of focal length 100 cm . Calculate power of concave lens.

A concave lens is kept in contact with a convex lens of focal length 20 cm. The combination behaves as a convex lens of focal length 50 cm . Find the power of concave lens.

An arrangement of two lenses consists of a converging lens of focal length 40 cm placed coaxially in contact with another lens of unknown focal length. The combination behaves like a diverging lens of focal length 40 cm. Find the power and nature of the second lens.

A concave lens is kept in contact with convex lens of focal length 20 cm. The combination works as a convex lens of focal length 50 cm. Find the power of concave lens.

A converging lens of focal length 40 cm is kept in contact with a diverging lens of focal length 30 cm. Find the focal length of the combination.

A convax lens of focal length 10.0cm is placed in contact with a convex lens of 15.0cm focal length ,What is the focal length of the combination.

A converging lens of focal length 50 cm is placed co-axially in contact with another lens of unknown focal length. If the combination behaves like a diverging lens of focal length 50 cm , find the power and nature of second lens.

A converging lens of focal length 5.0cm is placed in contact with a diverging lens of focal length 10.0cm. Find the combined focal length of the system.