Question

A point object $O$ is placed on the principle axis of a convex lens of focal length $20cm$ at a distance of $40cm$ to the left of it. The diameter of the lens is $10cm$. If the eye is placed $60cm$ to the right of the lens at a distance $h$ below the principle axis, then the maximum value of $h$ to see the image will be

• A. $2.5cm$
• B. $5cm$
• C. $0cm$
• D. $10cm$

Answer 1

The correct option is A $2.5cm$

In the following ray diagram ${\Delta }^{\prime }s,ABC$ and $CDE$ symmetric
So, $\frac{AB}{BC}=\frac{DE}{CD}\Rightarrow \frac{5}{40}=\frac{h}{20}\Rightarrow h=2.5cm$