Question

While performing an experiment on determining the focal length of a convex lens, a student obtains a sharp inverted image of the laboratory window grill on the screen and measures the distance between the screen and the lens. She then repeats the experiment and takes a distant tree as the object in the second case. In order to get a sharp image of the tree on the screen, she will now have to move the screen:
(1) slightly nearer to the lens
(2) slightly farther away from the lens
(3) very close to the lens
(4) very far away from the lens

Answer 1

The 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, she needs to move the screen towards the lens in order to obtain the focal point of the lens on the screen because the convex lens converges all the rays coming from a distant object at its focal point to form a real image.

Hence, the correct answer is option 1.