MPPSC 2017 General Studies Solved Paper-1

(A) The diopter is the unit of measure for the refractive power of a lens. The power of a lens is defined as the reciprocal of its focal length in metres, or D = 1/f, where D is the power in diopters and f is the focal length in metres. Lens surface power can be found with the index of refraction and radius of curvature.