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What is meant by power of a lens? Write its SI unit. A student uses a lensof focal length 40 cm and another of 20 cm. Write the nature and pewer ofeach lens. |
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Answer» The degree of convergence or divergence of a lens is expressed as power of the lens. It is the reciprocal of the focal length of the lens taken in metres. Its S.I. unit is Dioptre( D ). 1 Dioptre is defined as the power of a lens whose focal length is 1 m. Student A:40cmp=1/fp=1/0.4 (40cm=40/100m)p=1x10/4p=+2.5Dconverging or convex lens.Student B:f=20cmP=1/fp=1/0.2(20cm=20/100)p=1x10/2p=5Dconverging or convex lens |
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