text: I demonstrates the duality of wave/particle beahviour that characterises the Universe.\n\nIt is easier to do with electrons.\n\nIf you take two slits, and shine a light at them you will see a diffraction pattern beyond the slits, because the light waves alternately interfere constructively and destructively. \n\nThe same happens with electrons. Which shows that they behaves like waves.\n\nBut with electrons, you can arrange to fire them one at a time at the slits. So how on earth can they interfere? But the pattern seen to develop over time is precisely what is expected with the wave theory.