Q36 of 84 Page 322

State and define the SI unit of power of a lens.

The reciprocal of focal length of the lens is called the power of the lens (P).

P (in dioptre) =


The S.I unit of power of lens is diopter denoted by D.


From the formula of power of lens.


1 D =.


Thus 1 Dioptre is the power of the convex lens having focal length of 1m.


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