Final answer:
The power of a lens is the measure of its ability to converge or diverge light, calculated as the reciprocal of its focal length in meters, with the unit being diopters (1/m).
Step-by-step explanation:
The power of a lens is a measure of how much the lens converges or diverges light. It is calculated as the reciprocal of the focal length (f), where the focal length must be expressed in meters. Therefore, the power (P) of a lens in diopters (D) is given by the equation P = 1/f, with the understanding that 1 diopter equals 1/meter (1/m), also written as 1 m-1.
Optometrists use diopters to prescribe corrective lenses for spectacles and contact lenses, ensuring the necessary adjustment for an individual's vision. This concept of power differs from the concept of power in mechanics, represented in watts, which is a measure of the rate of energy transfer.
Negative power values, indicated by a negative focal length, correspond to diverging lenses, whereas positive values indicate converging lenses. It is essential to convert the focal length to meters before calculating the lens power.