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Calculate the radius of curvature of an equi-concave lens of refractive index 1.5, when it is kept in a medium of refractive index 1.4, to have a power of - 5 D ? |
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Answer» Solution :Here, `R_(1) =R_(2) = R` (say), `n_(L) = 1.5,n_(m) = 1.4` and POWER of lens P = `-5 D` `therefore P =1/f =(n_(L)/n_(m)-1)(1/R_(1) + 1/R_(2)) = (n_(L)/n_(m)-1).2/R` `RARR R = (n_(L)/n_(m)-1).2/P = (1.5/1.4 -1) xx 2/(-5) = 0.029m = 2.9 cm` |
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