 So putting a stream of particles through two slits, we wouldn't see an interference pattern. We just would have got a smear image from the two slits or mushed on top of each other. And if we put a wave through two slits, we do see an interference pattern. So Young used this to show that light was a wave. But you can also use this to tell whether other things are a wave or not. For example, you might be able to get an electron gun out of a really old television and fire them through two slits. And then you find out whether electrons are particles or waves. Now I'm going to show you a movie of someone done exactly that with electrons soon. But first, I want you to answer a very simple question. If you turn down the intensity of those electrons, if you turn down your electron gun that you've pulled out of an old television and you get a very small number of electrons landing on your screen, what is that going to look like?