First I want to admit that I'm not a physicist, but I'm very interested in physics. I have some questions about quantum mechanism that I haven't been able to find the answer through prolonged internet search, and I registered this site just to get answers to these questions. One of my question is regarding the electron slit experiment (or photon slit experiment alike). Online literature says that such experiment had been conducted that the electron pass through the slits one by one. My question is about the specifics of the experiments: Does every single electron shoot out of the electron gun go through the slit and form a dot at the backstop, or only some of them make it though? I think the answer is most likely no, but I'm not sure.