Hans Geiger studied radiation in a lot different experiments. He used a gadget known as the Geiger-Marsden experiment in one of his well-known tests. Geiger and his colleague Ernest Marsden used a thin gold foil as the target of an alpha particle beam in their experiment. The majority of the alpha particles, they found, were able to pass through the foil, although a little portion were deflected or even rebounded back. The results of this experiment showed an atom's dense, positively charged nucleus exists.