Question

If the total length of a concave mirror is $50cm$, then where should be an object is placed so that its image is two times and inverted

• A. $-55cm$
• B. $-75cm$
• C. $-65cm$
• D. $-85cm$

Answer 1

Answer: (B)

$-75cm$

Magnification, $m=\frac{f}{f-u}$
Here, $m=-2$ and $f=-50cm$
$\therefore -2=\frac{-50}{-50-u}\Rightarrow 100+2u=-50$
or $u=\frac{-150}{2}=-75cm$.