Question

The image formed by a concave mirror of focal length $6cm$ is $3$ times of the object, then the distance of the object from the mirror is

• A. $-4cm$
• B. $8cm$
• C. $6cm$
• D. $12cm$

Answer 1

The correct option is A $-4cm$

Image is $3$ times of the object.

$m=\pm 3$; magnification

and,

$f=-6cm$

Now,

$m=\frac{f}{f-u}$

$\Rightarrow \pm 3=\frac{-6}{-6-u}$

For real image-

$-3=\frac{-6}{-6-u}$

$\Rightarrow u=-8cm$

For virtual image-

$3=\frac{-6}{-6-u}$

$\Rightarrow u=-4cm$