Q. A point object $O$ is placed on the principal axis of a convex lens of focal length $20\ cm$ at a distance of $40\ cm$ to the left of it. The diameter of the lens is $10\ cm$. If the eye is placed $60\ cm$ to the right of the lens at a distance $h$ below the principal axis, then the maximum value of $h$ to see the image will be
A) 0
B) 5 $cm$
C) 2.5 $cm$
D) 10 $cm$
Explanation
(c) In the following ray diagram $\mathrm{\Delta}^{'}s,\ ABC$ and $CDE$ are symmetric
So, $\frac{AB}{AC} = \frac{DE}{CD} \Rightarrow \frac{5}{40} = \frac{h}{20} \Rightarrow h = 2.5\ cm$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.