1. A source of alpha radiation (radium) was placed in a lead box. The alpha radiation would be emitted from a slit in the lead box, aimed at the thin metal foil.
2. According to the plum pudding model, the positive alpha particles should pass through the foil and should not be greatly deflected, as seen in the picture to the right. In order to detect the alpha particles, a fluorescent screen made out of zinc sulfide was used. Each time that an alpha particle would hit the screen, a small flash of light would be detected. A microscope mounted above the screen allowed Geiger and Marsden to more accurately detect the flashes.
3. The two students could then measure the angle of deflection (the change of angle if the particle had gone straight through the foil).
