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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 pet er ofeach lens. |
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Answer» It is the reciprocal of the focal length of thelenstaken in metres. Its S.I. unit is Dioptre( D ). 1 Dioptre isdefinedas thepower of a lenswhose focal length is 1 m. Power of lens of focal length 40 cm=0.4 m=1/0.4=2.5 D Power of lens of focal length 20 cm=0.2 m=1/0.2= 5 D As both of the lenses have positive focal let, hence, both are convex lens or converging natured. |
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