A man can see distinctly from a distance of $0.5$ metre. If he wants to read a book placed at a distance of $25 c m$ , then what should be the power of lens ?

- 2.5 D

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- 1.5 D

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- 2 D

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+ 2 D

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Solution

The correct option is D $+ 2 D$
$d = 0.5 m$

$D_{2} = 25 m$

$\frac{1}{v} - \frac{1}{(- u)} = \frac{1}{f}$

$\frac{1}{25} - \frac{1}{50} = \frac{1}{f}$

$\frac{1}{f} = \frac{2 - 1}{50} = \frac{1}{50}$

$f = 50 c m$

$p = \frac{1}{f} = \frac{100}{50}$

$= 2 D$

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Similar questions

Q. A man can see distinctly from a distance of

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. If he wants to read a book placed at a distance of

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, then what kind of lens should he use?

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A person cannot see distinctly at the distance less than one metre. Calculate the power of the lens that he should use to read a book at a distance of 25 cm

[CPMT 1977; MP PET 1985, 88; MP PMT 1990]

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A man can see distinctly from a distance of 0.5 metre. If he wants to read a book placed at a distance of 25cm, then what should be the power of lens ?

The correct option is D +2Dd=0.5mD2=25m1v−1(−u)=1f125−150=1f1f=2−150=150f=50cmp=1f=10050=2D

A man can see distinctly from a distance of $0.5$ metre. If he wants to read a book placed at a distance of $25 c m$ , then what should be the power of lens ?

The correct option is D $+ 2 D$
$d = 0.5 m$

$D_{2} = 25 m$

$\frac{1}{v} - \frac{1}{(- u)} = \frac{1}{f}$

$\frac{1}{25} - \frac{1}{50} = \frac{1}{f}$

$\frac{1}{f} = \frac{2 - 1}{50} = \frac{1}{50}$

$f = 50 c m$

$p = \frac{1}{f} = \frac{100}{50}$

$= 2 D$