Question

A 5.0 diopter lens forms a virtual image which is 4 times the object placed perpendicularly on the principal axis of the lens. Find the distance of the object from the lens.

Answer 1

Given :

P= 5D

P=100/f

f=100/P= 100/5= 20cm

let height of object be ho

Then height of image= 4ho---> hi/ho=4

m=4

m=v/u=hi/ho

4= v/u

v=4u

from lens formula :

1/f=1/v-1/u

1/f-1/v= -1/u

1/20- 1/ 4u = - 1/u

1/20= 1/4u- 1/u

1/20= 1-4/4u

1/20 = -3/4u

4u= - 3x20

u= - 3x20/4= - 15cm

∴ object distance is 15cm

Answer 2

Hey!!

Refer the attachment !!

Thanks !