A lens of focal length f is used to project an image of a solar eclipse onto a flat sheet of paper. To get the clearest image, how far from the lens should be paper be?
A) f/2
B) f
C) 2f
D) more than 10f
E) less than f/10

Question

Quizplus · Accepted Answer

The clearest image of a distant object (like the sun) is formed at the focal length of the lens, so the paper should be placed at a distance equal to the focal length (f) from the lens.

A Lens of Focal Length F Is Used to Project