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If we need a magnification of 375 from a microscope of tube length 15 cm and an objective of focal length 0.5 cm, what focal length eye lens should be used ? |
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Answer» Solution :`M = - 375, L = 15 cm, f_(0) = 0.5 cm, f_(e) = ?, d = 25 cm` `M = (v_(0))/(-u_(0))(1 + (d)/(f_(e)))` As focal length of OBJECTIVE lens is small `u_(0) ~~ f_(0)`. ALSO, as focal length of EYE lens is small, `v_(0) ~~ L` `:. M = (L)/(- f_(0))(1 + (d)/(f_(e)))``- 375 = (15)/(- 0.5)(1 + (25)/(f_(e)))` `(25)/(f_(e)) = (375)/(30) - 1 = 11.5f_(e) = (25)/(11.5) = 2.2 cm` |
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