Question

when rays hit a thin foil of gold, very few particles are deflected back.what does it prove?

Answer 1

when rays hit a thin foil of gold, very few particles are deflected back then it proves that there is presence of positive charged particle at the centre of the nucleus.

Alpha particles are are positively charges particles that are made up of 2 protons, 2 neutrons and zero electrons.

So due to this when these positively charged rays strike on it they get repel as at the centre of the atom positively charged particle known as nucleus is present and due to this repulsion they get deflected back.