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A converging glass lens with a refractive index of 1.5 has a focal length of f in air. When it is completely immersed in a liquid of refractive index 2, its focal length and nature will be respectively (a) 2f and converging (b) 3f and converging (c) 2f and diverging (d) 3f and diverging |
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Answer» Correct Answer is: (c) 2f and diverging Let k = 1/R1 - 1/R2 . ∴ 1/f = (1.5 - 1)k and 1/f' = (1.5/2 - 1) k = (- 0.5/2) 2/f = - 0.5/f. ∴ f' = -2f. |
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