Concept:The power of a lens quantifies its ability to converge or diverge light rays, defined as the inverse of its focal length when measured in meters.
Explanation:The mathematical definition is
P=f1​, where
P is the power in diopters (D) and
f is the focal length in meters.
A lens with
f=1 m has a power of
1 D. A convex lens (positive power) converges light; a concave lens (negative power) diverges light.
This definition directly corresponds to option B: "The reciprocal of its focal length in meters."
Options A, C, and D do not match the standard definition in optics. The unit of power is the diopter, which only depends on focal length, not on refractive index or distances.
Answer:B. The reciprocal of its focal length in meters