Dioptric strength of the lens (convergence of the lens).
The power of the lens D is the reciprocal of the focal length expressed in meters.
The strength of the lens is expressed in reciprocal meters. Convergent lenses have positive optical power, and divergent lenses have negative dioptric power. The dioptric power of the lens is proportional to the refractive index of the lens. As the refractive index of the lens increases for equal radii of curvature, the dioptric power of the lens also increases.
We correct farsightedness ( hypermetropia ) with convergent plus lenses.
We correct myopia with divergent minus lenses.
Author: Prof. Emil Šatalić
