Question

The focal length of a concave mirror is $50\text{cm}$. Where should the object be placed so that the size of the image is two times the size of the object and inverted?

• A. $75\text{cm}$
• B. $60\text{cm}$
• C. $125\text{cm}$
• D. $50\text{cm}$

Answer 1

The correct option is A $75\text{cm}$

Since it is given that the size of the image is twice the size of the object, so in case of concave mirror, $m=-2$

Also $m=\frac{f}{f-u}$
$\Rightarrow -2=\frac{-50}{-50-u}$
$\therefore u=-75\text{cm}$