what is dioptre class 10

Dioptre is the SI unit of power of a lens, denoted by the letter D. One dioptre is defined as the power of a lens of focal length 1 metre. It is the unit of measurement of a lenss or curved mirror's optical power equal to the reciprocal of focal length (f) . The power of a lens is the ability of a lens to converge the rays falling on it.