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प्रश्न
Define 1 dioptre of power of a lens.
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उत्तर १
The SI unit of power of lens is dioptre which is denoted by the letter D. 1 dioptre is defined as the power of a lens of focal length 1 metre.
उत्तर २
1 dioptre is the power of a lens whose focal length is 1 metre.
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