Question

A concave mirror is said to have a real focus whereas a convex mirror is said to have a virtual focus. Why do you think this is so? Also mention which of the two - concave of convex lenses has a real focus?

Answer 1

When parallel light rays fall on a concave mirror, they meet at a point called the real focus. The image so formed can be taken on a screen. In convex mirrors, the rays diverge but appear to come from a point behind the mirror. The image cannot be taken on a screen. Hence, a concave mirror is said to have a real focus, whereas a convex mirror is said to have a virtual one. The convex lens, also known as a converging lens, has a real focus.