Question

A 4cm tall object is placed on the principal axis of a convex lens. The distance of the object from the optical centre of the lens is 12cm and a sharp image is formed at a distance of 24 cm from it on a screen on the other side of the lens. If the object is now moved a little away from the lens, in which way will we have to move the screen to get a sharp image of the object again? How will magnification be affected?

Answer 1

Image formation by convex lens at various object distances are as follows:
when object is at F- Image is produced at Infinity.
when object is at Infinity- Image will be formed at Focus.
when object is on 2F- image will be formed on 2F.
when object is beyond 2F- image formed will be between F and 2F
when object is between F and C---image formed will be beyond 2F.
based on the above observation, we can say that if we move the object little away from lens, the image moves towards the lens.
and size of the image reduces.
Conclusion: screen should be moved towards lens to focus the image of object.
magnification of the images becomes less.