Write expression for the focal length and power of a lens combination.

Write expression for power factor.

Write expression for the magnification produced by a lens system.

Define focal length of a lens

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

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.

What is the focal length of a convex lens of focal length 30cm in contact with a concave lens of focal length 20cm? Is the system a converging or a diverging lens? Ignore thickness of the lenses.

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.