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Define power and diopter |
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Answer» Power is degree of divergence and convergence of a lens its SI unit is diopter it is denoted by letter D. Power\xa0is defined as the rate of doing work. Power is measured in watt which is equal to joule per second.1 dioptre is SI unit of the power of a lens whose focal length is 1 metre. It is denoted by the letter D. Thus 1D = 1 m-1. Simply, when focal length ‘ f ‘ is expressed in metres, then, power is expressed in dioptres. The power of a convex lens is positive and that of a concave lens is negative. |
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