The Three Types of Radiation and their uses / properties: Alpha, Beta and Gamma

Certain isotopes decay over time. This decay of the atom emits three types of radiation, alpha, beta and gamma. The alpha and beta radiation are actual matter emitted by the atom, whereas gamma rays are very short wavelength electromagnetic waves. All of the radiation mentioned above are potentially hazardous to living tissue, but some more than others, as will be explained later on.

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The first type, Alpha, is made up of two neutrons and two electrons bound together identically to the nucleus of a Helium atom (ie. without the electrons). Alpha particles are very strongly ionising, meaning that if they come into contact with atoms in a living tissue it can cause mutations, unusual chemical reactions in the cell and possible cancer. Although they are the most ionsing, they are seen as the least dangerous out of radiation as long as it is not ingested or inhaled, this is because alpha radiation is stopped by even a sheet of paper or skin meaning that it cannot penetrate into your body. Alpha radiation is also stopped by a few centimetres of air, making it not too much of a hazard. Alexander Litvinenko was suspected to be killed by alpha radiation, but this was because it was believed to have been in his tea cup, administered by Russian ex-KGB officers. Alpha particles are deflected by a magnetic field.

There are many uses for the different types of radiation. Alpha particles are most commonly used in smoke alarms. This is where a tiny amount of Americium is decaying, emitting alpha radiation very locally between two sheets of metal. A small electric current is then passed through one of the plates, along the radiation and into the second plate. When the field of alpha radiation is blocked by smoke, the alarm is sounded. This alpha radiation is not harmless because it is very localised and any radiation that escapes will be stopped quickly in the air and would be extremely difficult to get into your body. This is also why people refer to an alarm as going ‘off’ because the continuous circuit of electricity has been turned/cut ‘off’ by the smoke, resulting in the alarm.

Beta radiation is made up of an electron with high energy and speed. Beta radiation is more hazardous because it can also cause ionisation of living cells. Although it is less ionising than Alpha radiation, it has the capability to pass through living cells and can be stopped by an aluminium sheet. If the particle hits a molecule of DNA it can cause spontaneous mutation and cancer.

Beta radiation is mainly used in industrial processes such as paper mills and aluminium foil production. A beta radiation source is placed above the sheets being passed out of the machines, these is then a beta radiation counter underneath (Geiger-Muller tube). Due to the fact that beta radiation can only partially go through paper and aluminium foil, depending on it’s thickness, this means the readings on the radiation counter are low, the foil is too thick and the presses are told to make it thinner and vice versa.

Gamma rays are high frequency, very short wavelength electromagnetic waves with no mass and no charge. They are emitted by a decaying nucleus so that it can let out energy that allows it to become more stabilised as an atom. Gamma rays have the highest penetrating power, only being stopped by a few centimetres of lead or a few metres of concrete, but some may still pass through because they are minutely small allowing them to pass through the vast areas of space between the nucleus of one atom and another. They are the least ionising of all the radiation but this doesn’t mean that they are not dangerous. Gamma rays are likely to be emitted along side alpha and beta radiation but some isotopes only emit gamma radiation.

Gamma rays are the most useful of the radiation because it can kill off living cells easily, without remaining in the substance, so this is used to sterilise some food because it passes through the food because it is dead but kills off the bacteria etc. Gamma rays are used in radiotherapy to kill off cancerous cells. They are also used to sterilise medical equipment, which is particularly useful in tools that would be melted by sterilisation or compromised by bleaches and other disinfectants. Gamma rays are also used to detect leaking pipes, gamma ray source is placed into the substance in the pipe (water etc.) then someone with a Geiger-Muller tube will count the radiation given off above ground, where the count spikes will be where the leak is because there is more of the substance in the ground there. Gamma rays are used because they can pass through the metal, rocks and other substances in the soil.

Radiocarbon dating is used to determine how old an object is that was once living tissue, this is not limited to animals and plants but also objects like string, rope and ships because these were all made from living tissue when they were made. The radioactive isotope used in carbon dating is Carbon 14, this is made when cosmic rays act on nitrogen in the upper atmosphere, turning it into carbon 14. Only one in every 850,000,000 carbon atoms are Carbon 14, but they can still be detected. All living cells take up carbon 14, whether it is from photosynthesis or eating other living cells. When a living cell dies, it stops taking in Carbon 14, because it stops photosynthesising or eating, and then gradually over time the Carbon 14 decays and is no longer found in the tissue. Carbon 14 is an emitter of beta particles and gamma rays. If we work out the half life of Carbon 14 (the time in which it takes from the radiation emitted from the source to be cut in half), which works out to be 5,730 years. This means that if we find a tissue that has 25% of the carbon 14 as in today’s atmosphere, we can date it as being 11,460 years old because 25% is half and half again, meaning that it has experienced two half lives. There are limitations and inaccuracies to carbon dating, for example we make the assumption that the amount of carbon 14 in the atmosphere back when the tissue was living, is the same as nowadays.

I hope this article has helped and if you have any questions, leave me a comment below and I will try to answer it either on the comments section or update the article to incorporate it! Thanks for reading!