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Double-convex lenses are to be manufactured from a glass of refractive index 1.53, with both faces of the same radius of curvature. What is the radius of curvature required if the focal length is to be 20 cm ? |
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Answer» SOLUTION :`(1)/(F) = (N - 1) ((1)/(R_(1)) - (1)/(R_(2)))` f= 20 cm , n = 1.55, `R_(1) = R, R_(2) = -R"therefore (1)/(20)= (1.55 - 1) ((1)/(R) + (1)/(R)) = 0.55 XX (2)/(R)` `R = 0.55 xx 2 x 20 = 22 ` cm |
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