Optical Power
A measure of a lens or curved mirror's degree of light convergence or divergence, equal to the reciprocal of its focal length.
Governing formula
P = 1 / f (in meters)
SI unit
Diopters (D, m⁻¹)
In depth
Convex converging lenses have positive optical power ($+P$); concave diverging lenses have negative power ($-P$). Powers of thin lenses in contact add linearly ($P_{total} = P_1 + P_2$).
Examples in the real world
A reading glass lens with a focal length of $+0.25 m$ ($25 cm$) having an optical power of $+4.0 Diopters$.