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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?
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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