Question

A convex lens is said to have a real focus and a concave lens a virtual focus .why? ( give a brief answer.)

Answer 1

A convex lens converges light rays on its focus whereas a concave lens diverges the light rays that seem to come from the focus therefore it is virtual.

Answer 2

A convex lens is said to have a real focus and a concave lens a virtual focus

        As we know a convex lens is also called converging lens the reason being it converges the light rays, coming from a source, on its focus. Hence the image thus formed will be called a real image because it is formed by converging of actual rays of light.

        A concave lens on the other hand is also called a diverging lens since the rays of light coming from a source diverges after passing through concave lens hence it appears to be coming from a point at which we see an image. The image is said to be virtual because it is not formed by actual converging of rays.