What unit is used to measure the refractive power of a lens?

The unit used to measure the refractive power of a lens is the diopter. This measurement indicates how strongly a lens can bend light rays, which is essential for correcting vision. A diopter is defined as the reciprocal of the focal length in meters; thus, if a lens has a focal length of 1 meter, it has a refractive power of 1 diopter.

This relationship is crucial in optometry as it allows eye care professionals to prescribe lenses that compensate for an individual's specific vision needs. The higher the diopter value, the stronger the lens and the more it can correct vision. Understanding this measurement is vital for fitting patients with the proper corrective lenses, ensuring they achieve optimal visual clarity.

The other units mentioned simply do not measure refractive power. Meters measure distance, Newtons measure force, and focal length refers directly to the distance at which light rays converge, without specifically quantifying the bending capability of the lens. Hence, diopter is the specific and appropriate unit for this context.