Q. A convex lens of focal length 30 cm produces 5 times magnified real image of an object. What is the object distance?
A) 36 cm
B) 25 cm
C) 30 cm
D) 150 cm
Explanation
(a) $\frac{1}{5u} - \left( \frac{1}{- u} \right) = \frac{1}{30}$
$\frac{1}{5u} + \frac{1}{u} = \frac{1}{30}$
$\frac{5 + 1}{5u} = \frac{1}{30}$
$u = 36\ cm$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.