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A converging lens has a focal length of 20 cm in air. It is made of a material of refractive index 1.6. If it is immersed in a liquid of refractive index 1.3, what will be its new focal length ? |
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Answer» Solution :Focal length of LENS in air f= + 20 cm, REFRACTIVE index of glass N = 1.6 and refractive index of LIQUID medium `n_m = 1.3`. If NEW focal length of lens be `f.` then: `f. = ((n-1)n_(m))/(n-n_(m))f = ((1.6-1) xx 1.3 xx 20)/(1.6 - 1.3) = (0.6 xx 1.3 xx 20)/0.3 = 52 cm` |
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