Alpha, Beta and Gamma Radiation

There are commonly said to be three types of nuclear radiation, labelled alpha, beta and gamma radiation respectively.

The alpha particle consists of two protons and two neutrons. It is a helium nucleus.

The beta particle is a fast moving electron. When a nucleus undergoes beta decay, another particle called an anti – neutrino is also emitted. In both these reactions the atom changes and becomes another element. When a nucleus undergoes gamma decay, the element does not change. The atom merely becomes less energetic.

All nuclear radiation is emitted when the nucleus undergoes some sort of decay. If it undergoes alpha or beta decay the atom changes from one element into another:

Alpha Decay:

Beta Decay:

Gamma decay:

Sometimes an element may undergo a series of decays one after the other. A simple example is shown below. The {}^60-27 Co nucleus undergoes a beta decay and two gamma decays. The half life of each decay is different.

The three types of radiation can be told apart by passing them though a magnetic field. Gamma radiation is not charged, hence it will not be affected by the field and will pass through undeflected. Alpha radiation and beta radiation are oppositely charged and will curl in opposite directions as predicted by the left hand rule. This is illustrated below.

Radioactivity is dangerous and can cause radiation sickness and kill. We need to protect ourselves from it.

Alpha radiation can be stopped very easily with a piece of paper or a few cm of air. However if it is swallowed it is the most deadly because all the radiation is absorbed by the body. Beta radiation can be stopped with a few cm of aluminium and gamma radiation is the most penetrating and needs several cm of lead.

The three types of radiation have their uses. Alpha radiation is used in smoke detectors, beta radiation is used to control the thickness of sheet metal and gamma rays are used to treat cancer.

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