A diverging lens has focal length 20 cm. An object of height 4 cm is placed 20 cm from the optical centre, in front of the lens. The image is formed at 10 cm away from it. The size of the image formed is

A diverging lens has focal length

20 cm

. An object of height

4 cm

is placed

20 cm

from the optical centre, in front of the lens. The image is formed at

10 cm

away from it. The size of the image formed is

2 cm

.
A diverging lens is also called a concave lens. It has a negative focal length.
Given

Focal length, f = - 20 cm,

Height of object, h_{1} = 4 cm

Object distance, u = - 20 cm

Image distance, v = - 10 cm

To find

image height, h_{2} = ?

By magnification formula, we know

\frac{h_{i}}{h_{o}} = \frac{v}{u}

\Rightarrow h_{i} = \frac{v}{u} \times h_{o}

\Rightarrow h_{i} = - \frac{10}{- 20} \times 4

h_{i} = 2 cm

A diverging lens has focal length $20 cm$ . An object of height $4 cm$ is placed $20 cm$ from the optical centre, in front of the lens. The image is formed at $10 cm$ away from it. The size of the image formed is