Question

Concave mirror of focal length is 10cm produces an image five time large and real .the distance of object form mirror will be

Answer 1

Answer:

12cm

Explanation:

f= -10cm

m=-5

-v/u=-5

v=5u

1/v+1/u=1/f

1/5u +1/u=1/-10

taking LCM

1+5/5u=1/-10

6/5u=1/-10

u=6*-10/5

u=-12cm

Answer 2

Answer:

The distance of object is $12cm$ from the middle.

Explanation:

$f=-10cm$

$m=-5$                          [image is $5$ times larger than the object]

⇒ $\frac{-v}{u}=-5$

⇒ $v=5u$

By mirror formula, we have

$\frac{1}{f}=\frac{1}{u}+\frac{1}{v}$

⇒ $\frac{1}{-10}=\frac{1}{u}+\frac{1}{5u}$                $[v:5u]$

⇒ $\frac{1}{-10}cm=\frac{5+1}{5u}$

⇒ $\frac{1}{-10}cm=\frac{6}{5u}$

⇒ $5u=6 \times (-10)cm$

⇒ $u=\frac{-60}{5}cm$

∴ $u=-12cm$

So, the distance of object is $12cm$ in front of the mirror.

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