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. ) A person needs a lens of power +2.5 D for correction of his vision(a) What kind of defect in vision is he suffering from?(b) What is the focal length of the corrective lens?(c) What is the nature of the corrective lens? |
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Answer» Power of lens = +2.5D , e.g., positive means lens is converging.A converging lens is convex lens . Hence person is using a convex lens for correcting his vision.Convex lens is used to correct myopia . A myopic eye, can't able to see distinct object clearly but can see nearby object clearly . the reason of this defect is elongation of eyeball and excessive curvature of the lens. Now, P = +2.5D P = 1/f ⇒f = 1/P = 1/2.5 m = 100/2.5 = 40cm Hence , focal length of convex lens is 40cm |
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