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Question
The near vision of an average person is 25 cm. To view an object with an angular magnification of 10, what should be the power of the microscope?
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Solution
It is given, that least distance of distinct vision of an average person (i.e., D) is 25 cm, in order to view an object with magnification 10,
Here, v = D = 25 cm and u = f
But the magnification `m = v/u = D/f`
⇒ `f = D/m = 25/10` = 2.5 cm = 0.025 m
But power `P = 1/(f("in" m)) = 1/0.025` = 40 D
This is the required power of lens.
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