Question

An object is placed at a distance of 15 cm from a convex lens of focal length 20 cm. List four characteristics (nature, position, etc.) of the image formed by the lens.

Answer 1

Given, object distance, u = -15 cm and focal length, f = 20 cm
Let image distance be 'v'.
We know, $\frac{1}{f}=\frac{1}{v}-\frac{1}{u}$
$\frac{1}{20}=\frac{1}{v}+\frac{1}{15}$
$\frac{1}{v}=\frac{1}{20}-\frac{1}{15}$
$\Rightarrow$ v = -60 cm.

Four characteristics of the image formed by the lens are:
(i) The image is virtual.
(ii) The image is erect.
(iii) Image is formed at a distance of 60 cm on the same side of the lens as the object.
(iv) The image is an enlarged image.