Question

A convergent beam of light is incident on a convex mirror so as to converge to a distance $12$ cm from the pole of the mirror. An inverted image of the same size is formed coincident with the virtual object. What is the focal length of the mirror

• A. $24$ cm
• B. $12$ cm
• C. $6$ cm
• D. $3$ cm

Answer 1

The correct option is C $6$ cm

Here object and image are at the same position. So, this position must be centre of curvature
$\therefore R=12cm$
$\Rightarrow f=\frac{R}{2}=\frac{12}{2}=6cm$