How is the power of a lens defined?

The power of a lens is defined as the reciprocal of its focal length. This means that if you know the focal length of a lens in meters, you can simply take the inverse to find the power. The formula P = 1/f explicitly states that the power (P) is equal to one divided by the focal length (f), underscoring that power is measured in diopters, where one diopter corresponds to a focal length of one meter.

A lens with a short focal length will have a higher power, indicating a stronger lens that can bend light more sharply, whereas a longer focal length results in lower power. This relationship is central to many applications in optics, such as designing corrective lenses and understanding how different lenses manipulate light.

The other choices do not accurately describe how lens power is defined, as they refer either to different concepts in optics or misinterpret the relationship between the physical properties of a lens and its optical power.