Alpha and Beta Particles in a Cloud Chamber скачать в хорошем качестве

Alpha and Beta Particles in a Cloud Chamber

This videos show the difference between tracks in a cloud chamber from alpha particles, which are bright white, dense, 1-inch long tracks created from Radon decay, and beta particles, which are thin, thread-line tracks left by high energy electrons created from muon decay. Cloud chamber tracks are created when an electrically charged particle passes through the alcohol fog near the bottom of the chamber. As it does, it ionizes some of the molecules along its path. These charged atoms attract surrounding atoms to them creating a line a droplets, which are large enough to see as tracks. The glass and metal walls of this cloud chamber block all outside alpha and beta particles. The only ones that can be seen are those produced inside the chamber itself. Radon is a naturally occurring radioactive gas produced from decaying Uranium in the Earth's crust. When Radon decays, it produces an alpha particle consisting of two neutrons and two protons. This is the same as a doubly ionized Helium atom. When the cloud chamber is first set up it contains air and therefore a few Radon atoms. Their decay is what produces the alpha particles. Because of their large size and +2 electrical charge, they interact very quickly with the alcohol atoms in the cloud chamber to produce short, solid tracks. Alpha tracks are short because the alpha particle reacts with so many alcohol atoms it looses it's energy very quickly. Cosmic rays from outer space react with the Earth's upper atmosphere to produce a shower of secondary particles, many of which are muons. These are high energy particles similar to electrons except they have 200 times as much mass. Because they are so small and have so much energy they can easily penetrate the walls of the cloud chamber. A few of them will decay either spontaneously or because they interact with one of the gas molecules in the chamber. When this happens they emit a beta particle and two gamma rays. The gamma rays can't be seen but the beta particle, an electron, can. Because it has a -1 electrical charge, it can ionize alcohol molecules as it passes near them. Because of its small size and charge, it doesn't interact as strongly as an alpha particle, so it leaves a much thinner, longer track. Its low weight means that it is easily turned. While some beta tracks are straight, many more and curved and follow irregular paths; even reversing direction.