Question

This image shows a stream of positively charged particles being directed at gold foil. The positively charged particles are called "alpha particles” and each one is like a nucleus without any electrons.

A laser source is shining red light onto a surface. Some bounces back at anges Some go straight through and some go through at an angle in both directions from the original path.
What is the best explanation for why a particle is striking point X?

Alpha particles are mostly empty space, so they move in random directions, and one of these alpha particles can strike point X.
The gold atoms contain negative electrons, so when alpha particles strike the gold they keep moving but in various directions.
If an alpha particle hits the gold foil, a gold nucleus splits and a particle from it flies out at point X.
When the dense, positive alpha particle passes close to a positive nucleus of gold, the alpha particle repels and hits the screen at point X.

Answer 1

Correct answer: "When the dense, positive alpha particle passes close to a positive nucleus of gold, the alpha particle repels and hits the screen at point X."

Explanation: Rutherford scattering shows most alpha particles pass through because atoms are mostly empty space, but a few are strongly deflected (even back) when they pass close to the small, dense, positively charged nucleus. The deflection is due to electrostatic (Coulomb) repulsion between the two positive charges. The other options are incorrect for the reasons stated (wrong cause or wrong mechanism).