Question

An object is placed infront of a converging lens of focal length 20 cm. The distance of the object from the lens is 30 cm. Find the position of the image formed.

Answer 1

Given:
The lens is a converging lens, i.e. a convex lens.
Focal length, $f=20cm$;
Object distance, $u=-30cm$

Let the image distance be $v$.

Using Lens formula,
$\frac{1}{v}-\frac{1}{u}=\frac{1}{f}$
$\frac{1}{v}-\frac{1}{-30}=\frac{1}{+20}$
$v=+60cm$

Therefore, the image will be formed at a distance of 60 cm on the other side of the optical centre of the convex lens.