Question

The power of a lens is . Define its principal focus and calculate its focal length.

Answer 1

Power of lens :

It is the amount of convergence or divergence produced by a convex lens or concave lens respectively

or

It can also be defined as the reciprocal of the focal length.

Its SI unit is Dioptre

P=

Answer 2

1/f=1/u-1/v

Hope u will understand