Types of Radiation

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Types of Radiation

There are three main types of radiation that can be emitted by radioactive particles. They are called alpha, beta, and gamma. All three types of radiation come from the nucleus of the atom. All three types of radiation will cause ionisation, but they behave slightly differently, because of the way they are made up.

Type of radiation Greek symbol What is it? Charge
Alpha α Particle - A highly energetic helium nucleus, containing 2 protons and 2 neutrons. Positive 2+
Beta β Particle - A highly energetic electron, released from inside a nucleus. It has negligible mass. When a beta particle is produced a neutron in the nucleus divides into a proton and an electron. It is the electron that is rejected from the nucleus at high speed that is the beta particle. Negative 1-
Gamma γ Wave - from the high frequency end of the electromagnetic spectrum. Waves have no mass. No charge

The diagram below shows the penetration of alpha, beta and gamma rays.

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The Table below explains why different types of radiation are absorbed by different things:

Beta These are small particles with a negative charge. They can ionise fairly easily so can only travel through thin materials before they are absorbed.
Gamma This is a wave that carries a huge amount of energy, but waves are not as good at ionising atoms as particles are. It is therefore really difficult to absorb them and they can even travel through thin lead and thick concrete.
Alpha These are large particles with a positive charge. They can ionise atoms really easily so quickly lose their energy by ionising nearby atoms. This means they can be absorbed by just a few centimetres of air, a sheet of paper or by skin.

Each type of radiation that can be emitted can be absorbed by different materials and ionises different amounts. They are equally dangerous but for different reasons.

Alpha particles:

Although alpha particles cannot penetrate the skin, if it gets into the body it can ionise many atoms in a short distance. This makes it potentially extremely dangerous. A radioactive substance that emits just alpha particles can therefore be handled with rubber gloves, but it must not be inhaled, eaten, or allowed near open cuts or the eyes.

Beta particles:

Beta particles are much more penetrating and can travel easily through skin. Sources that emit beta particles must be held with long handled tongs and pointed away from the body. Inside of the body beta particles do not ionise as much as alpha particles but it is much harder to prevent them entering the body.

Gamma waves:

These waves are very penetrating and it is almost impossible to absorb them completely. Sources of gamma waves must also be held with long handled tongs and pointed away from the body. Lead lined clothing can reduce the amount of waves reaching the body. Gamma waves are the least ionising of the three types of radiation but it is extremely difficult to prevent them entering the body.

When atoms disintegrate by radioactive decay, new daughter atoms are produced. We can work out which elements will be produced using decay equations. These are like the equations you may have used for chemical reactions. Each type of radiation has a chemical symbol that is used in the equation.

Note: the equations must always balance, so there are the same number of protons and neutrons on each side of the equation.

Types of Radiation

These equations are not likely to happen in real life, as usually a combination of alpha, beta and gamma are released rather than just one.

Here's an example for you to try:

A uranium atom decays releasing an alpha particle and a beta particle, what will the final daughter atom be?

Lets do this in two steps:

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