Types of radiation
Three types of ionising radiation are:
Alpha particle
A type of ionising radiation consisting of 2 protons and 2 neutrons. particle \(\alpha\) - is a helium nucleus, two protons and two neutrons. It has a large mass, compared to other ionising radiations, and a strong positive charge.
Beta particle
A type of ionising radiation consisting of a single electron. particle \(\beta\) - is a fast moving electron. It has a very small mass and a negative charge.
Gamma ray
Gamma ray \(\gamma\) - is a high-energy electromagnetic wave. The shortest wavelength and highest energy part of the EM spectrum. Produced by radioactive materials. are caused by changes within the nucleus. They are part of the The different types of electromagnetic radiation, arranged in order of frequency or wavelength. and so travel at the speed of light. They have no mass and no charge.
Penetrating power
Each type of radiation has a different ability to penetrate materials. The material is said to have absorbed the radiation.
The energy of the three radiations is absorbed by the material through which the radiation passes. The amount of energy which is absorbed depends on the type of radiation and the type of the absorbing material.
- The range of the alpha radiation in an absorbing material is less than that of beta or A type of ionising radiation that is also part of the EM spectrum. It has no mass.. The alpha radiation transfers more energy to an absorber than beta or gamma radiation. Alpha radiation is absorbed by the thickness of the skin or by a few centimetres of air.
- Beta radiation is more penetrating than alpha radiation. It can pass through the skin, but it is absorbed by a few centimetres of body tissue or a few millimetres of aluminium.
- Gamma radiation is the most penetrating of the three radiations. It can easily penetrate body tissue. It requires several centimetres of lead or about 1 metre of concrete to absorb it.
| Radiation | Range (cm) | Ionising power | Can pass through paper? | Can pass through 5mm of aluminium | Can pass through 5cm of lead? | Electrical field deflection |
| Alpha | 3-5 | Highly ionising | No | No | No | Deflected towards negative plate |
| Beta | about 15 | Ionising | Yes | No | No | Deflected towards positive plate |
| Gamma | much longer | Weakly ionising | Yes | Yes | No - although some will still get through | None |
| Radiation | Alpha |
|---|---|
| Range (cm) | 3-5 |
| Ionising power | Highly ionising |
| Can pass through paper? | No |
| Can pass through 5mm of aluminium | No |
| Can pass through 5cm of lead? | No |
| Electrical field deflection | Deflected towards negative plate |
| Radiation | Beta |
|---|---|
| Range (cm) | about 15 |
| Ionising power | Ionising |
| Can pass through paper? | Yes |
| Can pass through 5mm of aluminium | No |
| Can pass through 5cm of lead? | No |
| Electrical field deflection | Deflected towards positive plate |
| Radiation | Gamma |
|---|---|
| Range (cm) | much longer |
| Ionising power | Weakly ionising |
| Can pass through paper? | Yes |
| Can pass through 5mm of aluminium | Yes |
| Can pass through 5cm of lead? | No - although some will still get through |
| Electrical field deflection | None |
Each type of radiation is caused by a decay (either spontaneous - natural - or induced - a reaction has caused the decay).
The nuclei of some atoms are unstable, and will naturally undergo 'radioactive decay'. This causes the release of ionising radiation which allows the nucleus to become more stable.
Atoms that do this are said to be radioactive.
A comparison of alpha, beta and gamma
