Fire at the Gold Foil

Interactive Simulator · The Alpha-Scattering Experiment

Over a hundred years ago, scientists fired tiny positive alpha particles at a very thin sheet of gold. Almost all went straight through, which means the atom is mostly empty space. A few were pushed off to the side, and the odd one bounced almost straight back, which can only happen if there is a tiny, heavy, positive lump at the centre: the nucleus. Aim your alpha particle to land it in the target detector.

Mission Aim so the alpha lands in the target detector (44°). Round 1 Streak 0 Best 0

Aim: distance from the nucleus 3.0

Compared with the target, this alpha will deflect:

Alpha particles are streaming at the foil; watch how most pass straight through. Set your aim, predict, then fire.

deflection angle?

target detector44°

what it showsaim and fire

Closer to the nucleus means a bigger push, so a bigger deflection. A head-on aim bounces almost straight back.