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InterviewSolution
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The radii of curvature of the surfaces of a double convex lens are `20 cm and 40 cm` respectively, and its focal length is `20 cm`. What is the refractive index of the material of the lens ? |
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Answer» Here, `R_1 = 20 cm, R_2 = -40 cm, f = 20 cm, mu = ?` As `(1)/(f) = (mu - 1)((1)/(R_1) - (1)/(R_2))` `:. (1)/(20)=(mu - 1)((1)/(20) + (1)/(40)) = (mu - 1) (3)/(40)` or `(mu - 1) = (2)/(3)` or `mu = (2)/(3)+ 1 = (5)/(3)`. |
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