Write a note on power of lens.

Power of lens is defined as the efficiency with which a lens can converge or diverge the light ray.

The reciprocal of focal length of the lens is called the power of the lens (P).

P (in dioptre) =

The S.I unit of power of lens is dioptre denoted by D.

Power of convex lens is taken as positive and of concave lens is negative. The instrument used for measuring the power of lens is called dioptremeter.