Annu and Anand have concave and convex lenses respectively. They took lenses in sunlight and tried to burn two pieces of paper of equal areas and temperature . State which lens will burn the paper. Give the reason. Explain with the help of a diagram, why the other paper did not burn.

Explanation

The convex lens will burn the paper. See figure for reference. The ray of sunlight will converage at the principal focus of the lens. Hence, if the paper is held at the focus, it will burn due to concentration of heat energy.

(2) The paper held in front of the concave lens, will not burn. For reference, see fig. Teh concave lens will diverage the rays of sunlight falling on it. Hence, the paper will not burn.