Focal length of concave lens shown in figure is 60 cm. Find image position and its magnification.

Explanation

For the given situation,
`u=-30cm, f=-60cm`
Using the lens formula, we have
`1/v-1/-30=1/-60`
Solving this equation, we get
`v=-20cm`
Further, `m=v/u=(-20)/(-30)=+(2)/(3)`. Point b is `2mm` above the principal axis. Therefore, its image b'
will be `(2)((2)/(3))` or `4/3mm`, above the principal axis.
Similarly, point a is 1mm below the principal axis. therefore, its image a' will be `(1)((2)/(3))` or `2/3mm` below the principal axis. The final image is as shown in fig. `31.67`