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A pin of length 2 cm is placed perpendicular to principal axis of a converging lens.An inverted image of size 1 cm is formed at a distance 40 cm from the pin . Find the focal length of the lens and it's distance from the pin? |
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Answer» h = 2 cm h' = 1 cmimage is inverted => image is real. m = - V/u = h'/h = -1/2 u = - 2 v u is negative and v is positive -u + v = 40 cm 3 v = 40 cm => v = 40/3 cm u = - 80/3 cm 1/F = 1/v - 1/u = 3/40 + 3/80 = 9/80 f = 80/9 cm |
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