A point object is placed at a distance of $x$ cm from a convex mirror of focal length $40 c m$ . Image is formed $20 c m$ behind the mirror. Find $x$ .

20 cm

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30 cm

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10 cm

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40 cm

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Solution

The correct option is D 40 cm
$v$ = +20 cm
$f$ = +40 cm
$\frac{1}{v} + \frac{1}{u} = \frac{1}{f}$
$\frac{1}{20} + \frac{1}{u} = \frac{1}{40}$
$\frac{1}{u} = \frac{1}{40} - \frac{2}{40}$
$u = - 40$ cm
or $x = 40$ cm

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A point object is placed at a distance of x cm from a convex mirror of focal length 40 cm. Image is formed 20 cm behind the mirror. Find x.

The correct option is D 40 cmv = +20 cm f = +40 cm 1v+1u=1f 120+1u=140 1u=140−240 u=−40 cm or x=40 cm

A point object is placed at a distance of $x$ cm from a convex mirror of focal length $40 c m$ . Image is formed $20 c m$ behind the mirror. Find $x$ .

The correct option is D 40 cm
$v$ = +20 cm
$f$ = +40 cm
$\frac{1}{v} + \frac{1}{u} = \frac{1}{f}$
$\frac{1}{20} + \frac{1}{u} = \frac{1}{40}$
$\frac{1}{u} = \frac{1}{40} - \frac{2}{40}$
$u = - 40$ cm
or $x = 40$ cm