A convex lens made of glass (µ = 1.5) has both radii of curvature 20 cm each. A point object is placed on the principal axis at a distance of 40 cm from the lens. The distance of the image from the lens is:

40 cm

The correct answer is Option (3) → 40 cm

According to len's Maker formula -

$\frac{1}{f}=(μ-1)\left(\frac{1}{R_1}-\frac{1}{R_2}\right)$

$⇒\frac{1}{f}=(1.5-1)\left(\frac{1}{20}-\frac{1}{20}\right)=\frac{1}{20}$

$⇒f=20cm$

On using the lens formula

$\frac{1}{f}=\frac{1}{v}-\frac{1}{u}$

$⇒\frac{1}{20}=\frac{1}{v}-\frac{1}{-40}⇒v=40cm$