Power of lens: The degree of convergence or divergence of light rays obtained by a lens is expressed in terms of its power. Power of a lens is defined as the reciprocal of its focal length.
p = 1/f
S.I. unit of power of a lens is ‘dioptre’
If the power of lens, P = +2 D.
Lens is convex and the focal length of the lens is +0.50 m.