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.

Two thin converging lenses of focal lenths 15 cm and 30 cm are held in contact with each other.Calculate power and focal length of the combination.

Two lenses f powers-1.5 and +2.75 D are kept in contact.Find the focal length of the combination.

Define focal length of a lens

Two thin lenses of focal length f_1 and f_2 are placed in contant .The focal length of the composite lens will be

Two lenses of powers+15D and -5D are in contact with each other. What is the focal length of combination?

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.

Two lenses of focal length 10 cm and -20 cm are placed in contact .What is the total power of the combination?