If the focal length of a lens is "f" then its reciprocal "1/f" is called the power of the lens.

Power of the lens=p=1/f

When "f" is measured in meters then power of the lens is in 'Dioptres'. The unit of power 'Dioptres' is defined as;

"Power of a lens is one Dioptres when its focal length is one meter". Its symbol is "D".

hyperphysics.phy-astr.gsu.edu

Power of the lens=p=1/f

When "f" is measured in meters then power of the lens is in 'Dioptres'. The unit of power 'Dioptres' is defined as;

"Power of a lens is one Dioptres when its focal length is one meter". Its symbol is "D".

hyperphysics.phy-astr.gsu.edu