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 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.

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 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.

A converging and a diverging lens of equal focal lengths are placed co-axially in contact. Find the power and the focal length of the combination.

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.