Q. The focal length of convex lens is $30\ cm$ and the size of image is quarter of the object, then the object distance is
A) $150\ cm$
B) $60\ cm$
C) $30\ cm$
D) $40\ cm$
Explanation
(a) $m = \frac{f}{f + u} \Rightarrow - \frac{1}{4} = \frac{30}{30 + u} \Rightarrow u = - 150\ cm$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.