Question

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

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

Answer 1

The correct option is A -4 cm

$m=\pm 3$ 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 $3=\frac{-6}{-6-u}\Rightarrow u=-4cm$