Question

When sunlight is concentrated at a paper placed at the principal focus of a convex lens, the paper burns off. Why is that so???

Answer 1

because all the rays are brought together at a one point if they are concave they spread the rays but convex is quite opposite to concave so whenever sunlight is concentrated at a paper placed at the principal focus of convex lens the paper burns

Answer 2

CONVEX LENS IS ALSO CALLED AS REFRACTING LENS..........which means............. it concentrates all the light at principal focus..... as concentration of light increases at one point............ it becomes hot and burns.