Q. A virtual image three times the size of the object is obtained with a concave mirror of curvature $36\ cm$. The distance of the object from the mirror is
A) 5 $cm$
B) 12 $cm$
C) 10 $cm$
D) 20 $cm$
Explanation
(b) Image is virtual so $m = + 3$ and $f = \frac{R}{2} = 18\ cm$
So from $m = \frac{f}{f - u} \Rightarrow 3 = \frac{( - 18)}{( - 18) - u} \Rightarrow u = - 12\ cm$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.