7.15 describe the results of Geiger and Marsden's experiments with gold foil and alpha particles

In an attempt to disprove the plum pudding model, Geiger and Marsden set up an experiment in which  they positioned a sheet of gold foil in a circle of zinc sulphide screen. They then aimed alpha particles at a sheet of thin gold foil. They concluded that most of the alpha particles went straight through the foil, and gave a tiny flash (a scintillation) when they hit the zinc sulphide screen. However, some of the alpha particles were deflected at 90º to the direction they were traveling, and some came straight back. This concluded that inside an atom there must be positively charged nuclei which repel the alpha particles (this is why they 'bounce off' at different directions).