Question

A student obtained a sharp image of the grill of a window in the laboratory on a screen, using a convex lens. For getting better results, her teacher suggested focussing of a distant tree instead of the grill. In which direction should the lens be moved for this purpose to get a sharp image on the screen?
(1) Towards the screen
(2) Away from the screen
(3) Behind the screen
(4) Very far away from the screen

Answer 1

Grill of the window is a nearby object for the lens, so the image would form away from the focal point of the lens. Now, to obtain the image of a distant tree, he needs to shift the lens towards the screen to have the focal point on the screen. Because the convex lens converges all the rays coming from a distant object to its focal point.

Hence, the correct answer is option 1.