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A lens of focal length 12 cm forms an erect image three times the size of the object. The distance between the object and image is :(a) 8 cm (b) 16 cm (c) 24 cm (d) 36 cm |
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Answer» (b) 16 cm Magnification, m = v/u 3 = v/u v = 3u Lens formula : 1/v - 1/u = 1/f 1/3u - 1/u = 1/12 -2/3u = 1/12 u = -8 cm v = 3 x -8 = -24 cm Distance between object and image = u - v = -8 - (-24) = -8 + 24 = 16 cm |
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