Question

A converging lens of focal length 20 cm is placed in contact with, and to the left of, a diverging lens of focal length 30 cm. If an object is placed 40 cm to the left of the converging lens, the total magnification is: Group of answer choices –1.0 –3.0 +2.0 –1.5 +3.0

Answer 1

Magnification will be equal to 3

Step-by-step explanation:

We have given focal length of the converging lens
`F_1=20cm`

Focal length of the diverging lens
`F_2=30cm`

Object is placed 40 cm to the length of the converging lens d = 40 cm

Combination of the focal length will be equal to

`(1)/(F)=(1)/(F_1)+(1)/(F_2)`

`(1)/(F)=(1)/(20)+(1)/(-30)=(1)/(20)-(1)/(30)=(1)/(60)`

F = 60 cm

So combination of the focal length will be 60 cm

Magnification is given by

`M=(F)/(F-d)=(60)/(60-40)=3`

So magnification will be equal to 3