If the focal length of a lens fis in cm, then write the formula of power of lens.

The focal length of the combination of two thin lenses in contact is 80 cm. If the focal length of one lens is -20 cm, what is the power of the other lens ?

If the focal length of the biconvex lens is 25 cm, then the power of the lens will be

The focal length of a lens is -50 cm. The nature and power of the lens is

If the focal length of a converging lens is 50 cm. What is the power of the Lens ?