Question

A convex lens can burn a piece of paper using sunlight. give reason

Answer 1

convex lens are also called as converging lens.

When beam of Sunrays parallel to principal axis are incident on convex lens it will converge the rays at focus on paper, if paper is exposed to sunlight.
hence convex lens can burn a piece of paper

Answer 2

Convex Lens Concentrates The Light Energy To One Spot On The Paper So That The Heat  Energy Accumulates On That One Small Spot Of Paper.

As The Heat Increases, Combustion Will Occur When The Spot Becomes Too Hot & The Paper Burns.

Hope It Will Help you ! ..

Please Mark It as Brainliest answer !