Final answer:
The refractive power (P) of a lens is the inverse of its focal length (f). The relationship is given by the equation P = 1/f, where the focal length is measured in meters.
Step-by-step explanation:
The refractive power, P, of a lens is related to its focal length, f, by the simple relationship P = 1/f. This means that the power of a lens is the inverse of the focal length. When focal length is expressed in meters, this gives the power in diopters, which is the unit of measurement for the refractive power of lenses. For example, a lens with a focal length of 0.5 meters has a power of +2 diopters, because 1 divided by 0.5 equals 2. The shorter the focal length, the more powerful the lens is, and consequently, it will focus light rays into a smaller and more intense spot.