Question

An image is formed at a distance of $12\text{cm}$ from a concave mirror. The image formed is real and four times larger than the object. Calculate the object distance from the mirror.

• A. $-3\text{cm}$
• B. $+3\text{cm}$
• C. $-12\text{cm}$
• D. $+12\text{cm}$

Answer 1

The correct option is A $-3\text{cm}$

We know that, magnification,
$m=\frac{-v}{u}$

$\Rightarrow -4=\frac{-(-12)}{u}\left[\text{For real and inverted}\right]$

$\Rightarrow u=-3\text{cm}$