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A hypermetropic person whose near point ...

A hypermetropic person whose near point is at `100 cm` wants to read a book at `25 cm`. Find the nature and power of the lens needed.

Text Solution

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Here, `u = - 25 cm, v = - 100 cm`,
`f = ?`
As `(1)/(f) = (-1)/(u) + (1)/(v)`
`:. (1)/(f) = (1)/(25) - (1)/(100) = (4 - 1)/(100) = (3)/(100)`
`f = (100)/(3) cm = 33.3 cm`
`P = (100)/(f) = (100)/(100//3) = 3` dioptre
The lens must be converging.
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