Saturday, September 27, 2008

Radioactivity--Alpha and Beta Particles...Gamma Rays

An Alpha particle is like the nucleus of the Helium atom. It has two neutrons and two protons bound together. Because of its composition, it has a much greater mass than the Beta particle which has the mass of an electron. Alpha particles have minimal penetrating ability. They are absorbed by a sheet of paper. However, their ability to ionize is extremely high (Ionization means their ability to break molecular bonds and to remove electrons from atomic orbits). The bottom line is, they are not able to penetrate materials but they do a lot of damage close to the point where they originate.

Negative Beta particles are similar in mass and charge to electrons. And although they have greater penetrating ability than Alpha particles their range is still limited. They can be absorbed by a sheet of aluminum foil. Beta particles cause ionization, but not as significant as Alpha particles. Beta particles vary widely in energy. Their ability to ionize depends on their Kinetic Energy as they leave the nucleus. In general, the ionization produced by Beta particles is spread out over a greater distance from the source (point of origin) than Alpha particles, but still in a localized area around the source.

Gamma rays originate in the nucleus as a product of radioactive decay, but they are quite different from Alpha and Beta particles. They are a member of the Electromagnetic spectrum. Therefore, they travel at the speed of light, and consist of photons which have no mass. Gamma rays have the ability to penetrate long distances from the source. It takes at least 7cm of lead to absorb Gamma rays. They are able to ionize material that is at a great distance from the source. However, their ionizing ability is less than that of Alpha and Beta particles.

1 comment:

Tania said...

In watching this demonstration I noticed the word ionization was mispelled. I believe the correct spelling is ionization.