Question

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. 5 cm
• B. 2.5 cm
• C. 10 cm

Answer 1

The correct option is B 2.5 cm

In the following ray diagram ${\Delta }^{\prime }s,ABC$ and CDE are symmetric

So, $\frac{AB}{BC}=\frac{DE}{CD}\Rightarrow \frac{5}{40}=\frac{h}{20}\Rightarrow h=2.5cm$