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An object is kept at 60 cm in front ofa convex lens. Its real image is formed at 20 cm from the lens . Find the focal length and power of the lens. |
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Answer» Solution :DATA : Convexlens , `u=-60`cm, `v=20` cm, `f=` ? `1/f =1/v -1/u =1/(20 cm) - 1/(-60cm) =(1)/(20 cm) +(1)/(60 cm)` `=(3+1)/(60 cm) +(4)/(60 cm) =(1)/(15 cm)` `therefore f=15 cm` The focal length of the LENS =15 cm. |
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