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A farsighted person's least distance of distinct vision is 0.5 m. The power of the lens that shouldbe prescribed to enable him to read a book held at 0.25m is + x diopter. Find the value of x.Space for Rough Work |
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Answer» A long sighted person means that he can see distant object clearly but he cannot see objects near to him .This defect is also known as Hypermetropia. Given :v=-50cmu=-25cm(normal near point)focal length=?Lens formula:1/f=1/v-1/u1/f=1/-50 -1/-25=1/25-1/50=2-1/50=1/50f=50cmHence convex lens of focal length 50cm should be advised or used to correct this defect. |
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