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

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.

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 of focal length 20cm is placed in contact with a convex lens of focal length 40cm. Find the power of the combination.

A converging lens of focal length 30 cm is placed in contact with another converging lens of unknown focal length, then possible value for focal length of combination is

A converging lens of focal length 30 cm is placed in contact with another converging lens of unknown focal length, then possible value for focal length of combination is

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.

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.

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.