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Gamma decay is one of three main types of radioactive decay. The other two are alpha and beta. In gamma decay, particles known as gamma rays are emitted. Gamma rays are actually high energy photons, the particle analogue of an electromagnetic wave.
First of all, what is a radioactive decay? Well, we can start by saying that radioactive substances are highly unstable. As such, they strive to attain stability and in the process, undergo what is known as radioactive decay. You can think of a radioactive substance as being made up of highly unstable nuclei (made up of protons and neutrons). It is actually these nuclei that undergo radioactive decay.
When each unstable nucleus decays, it loses a great amount of energy. This energy can come in the form of either an alpha particle (a Helium nucleus), a beta particle (an electron or positron), or a gamma particle (also known as a gamma ray). When a gamma particle is the one emitted, then the decay is known as a gamma decay.
While alpha and beta decays occur because there are either too much neutrons compared to protons or too much protons compared to neutrons in the nucleus (this is why the nucleus is unstable), gamma decay simply occurs because the nucleus is in an excited or highly energetic state and hence has to ‘relax’ a bit.
When this nucleus jumps down to a less energetic state, it releases the unwanted energy in the form of an electromagnetic wave which, as stated earlier, is the gamma ray.
Among all three emitted particles in radioactive decay processes, gamma particles are the most penetrating. While alpha particles can be stopped by a sheet of paper and beta particles, by an aluminum plate, gamma particles can only be stopped by a thick dense material such as lead. Reminds you of Superman, does it?
Because of the high penetrating capabilities of its emitted particles, gamma decay is considered the greatest threat among the three. Radioactive substances in laboratories are kept inside Lead-sealed cabinets. Some even have Lead-sealed lab rooms. This design is made specifically for the purpose of preventing gamma rays from passing through.
Gamma rays that strike human cells can dislodge electrons from atoms comprising the cells because of the rays’ ionizing property. This can leave the atom with a positive charge, causing it to interact with other atoms beside it and subsequently damaging the cell.
We have some related articles here in Universe Today. Here are the links:
Here are the links of two more articles from SLAC:
- Theory: Radioactive Decays (SLAC VVC)
- SLAC Today – in Word of the Week: Radiation article
Here are two episodes at Astronomy Cast that you might want to check out as well:
- Avoiding the Heat Death, Orbiting Galaxies, and the Dangers of Space Radiation
- Hidden Fusion, the Speed of Neutrinos, and Hawking Radiation