Q. An object is placed at a distance 20 cm from the pole of a convex mirror of focal length 20 cm. The image is produced at
A) 13.3 cm
B) 20 cm
C) 25 cm
D) 10 cm
Explanation
(d) $u\ = \ - 20\ cm,\ f = \ 20\ cm$
From mirror formula,
$\frac{1}{f} = \frac{1}{v} + \frac{1}{u}$
$\frac{1}{20} = \frac{1}{v} + \frac{1}{- 20}$
$\frac{1}{v} = \frac{1}{20} + \frac{1}{20}$
$\frac{1}{v} = \frac{2}{20} \Rightarrow v\ = \ 10\ cm$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.