Question

An object is placed at 40 cm from the optic centre of a convex lens on its principal axis. if the focal length of the lens is 24 cm, find how far from the lens the screen should be placed to obtain a well-defined image.

• A. 48 cm
• B. 38 cm
• C. 50 cm
• D. 60 cm

Answer 1

The correct option is D 60 cm

given: $u=-40cm$
$f=24cm$
solution:from lens formula
$\frac{1}{v}-\frac{1}{u}=\frac{1}{f}$
$\frac{1}{v}+\frac{1}{40}=\frac{1}{24}$
$\frac{1}{v}=\frac{1}{24}-\frac{1}{40}=\frac{16}{960}=\frac{1}{60}$
$v=60cm$