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Diameter of plano - convex lens is 6 cm and thickness at the centre is 3 mm. If speed of light in material of lens is 2 xx 10^(8) m//s, the focal length of the lens is : |
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Answer» Solution :(b) `R^(2) = d^(2) + (R - t)^(2)` `R^(2) - d^(2) = R^(2) {1-(t)/(R)}^(2)` `1 - (d^(2))/(R^(2)) = 1-(2t)/(R )` `R=((3)^(2))/(2xx(0.3))=(90)/(6) = 15 cm` `(1)/(F) = (mu-1)[(1)/(R_(1))-(1)/(R_(2))]` `(1)/(f) = ((3)/(2) - 1) ((1)/(15))` 
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