Q. A convex lens of focal length $\ \frac{1}{3}\ m\ $forms a real, inverted image twice in size of the object. The distance of the object form the lens is
A) 0.5 m
B) 0.166 m
C) 0.33 m
D) 1 m
Explanation
(a) $m = \frac{f}{f + u} = - 2 = \frac{\frac{1}{3}}{\frac{1}{3} + u}$
$- \frac{2}{3} - 2u = \frac{1}{3}$
Or $\ - 2u = \frac{1}{3} + \frac{2}{3} = 1$
Or $\ u = - \frac{1}{2}m = - 0.5\ m$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.