Question

A boy was about to use magnifying glass to look at the sun but her mother immediately stopped him. Why?

Answer 1

magnifying glass is a convex lense.When parallel rays of light pass through a convex lens the refracted rays converge at one point which is called the principal focus.now if the UV rays of the sun are converged at a point , the principal focus would become extremely hot and Harm the point.Therefore,the eyes would be harmed or effected negatively. So his mother stopped him.
Now...here is a good activity which is dangerous you shouldn't try it, it is use a paper and a magnifying glass in front of the sun.The observation would be the paper will burn.
Therefore it shows it's very harmful.