Question

A child while playing in ground with a convex lens observes that a paper begins to burn when sun rays are made to fall on it through the lens. explain this with the help of diagram

Answer 1

This is because the lens with he is playing is a convex lens which is actually a converging lens. It converges all the light rays in a single point when turned at 45° so that it can give high amount of heat at a single point, due to this heat the paper starts to burn.