A concave lens has focal length of $10 cm$ . If the object is placed at a distance of $30 cm$ from the lens, then the magnification produced by the lens is

1.33

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0.25

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0.84

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1.25

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Solution

The correct option is B $0.25$
Here,
Object distance, $u = - 30 cm$
focal length, $f = - 10 cm$

Using formula,
$\frac{1}{v} - \frac{1}{u} = \frac{1}{f}$
$\Rightarrow \frac{1}{v} - \frac{1}{(- 30)} = \frac{1}{(- 10)}$
$\Rightarrow v = - 7.5 cm$

So, magnification, $m = \frac{v}{u} = \frac{- 7.5}{- 30} = 0.25$

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A concave lens has focal length of 10 cm. If the object is placed at a distance of 30 cm from the lens, then the magnification produced by the lens is

The correct option is B 0.25Here, Object distance, u=−30 cm focal length, f=−10 cm Using formula, 1v−1u=1f ⇒1v−1(−30)=1(−10) ⇒v=−7.5 cm So, magnification, m=vu=−7.5−30=0.25

A concave lens has focal length of $10 cm$ . If the object is placed at a distance of $30 cm$ from the lens, then the magnification produced by the lens is