Radiation surrounds us everywhere in our day-to-day lives. Examples include the ultraviolet rays given off by the sun, the visible light we are able see and the x-rays used in medicine.

Radiation can be classified as either ionising or non-ionising. The different types of radiation are classed based on how much energy it has. Ionising radiation refers to radiation that has enough energy to break an electron away from an atom, a process called ionisation.

Because ionising radiation has enough energy to remove electrons from atoms, it has the ability to change the chemical composition of the material it interacts with. In living tissue this effect can result in a process that damages DNA and can result in the death or mutation (cancer) of the impacted cell. Larger doses of ionising radiation can cause deterministic effects such as skin burns, radiation sickness or worse.

Ionising radiation surrounds us everywhere in everyday life and is completely unavoidable and is safe at low doses. Living in Australia for one year will expose you to an average of 1.7 mSv of background radiation – an amount that is completely safe to receive every year during your life. A dose 1000 times larger than this annual average would be required to cause harmful deterministic effects.

In our daily lives we are exposed to ionising radiation from both natural and artificial sources. Examples include the radioactive isotopes present in bananas and in soil as well medical x-rays and the sun.

There are three main types of ionising radiation:

X-rays and gamma rays, like the rest of the electromagnetic spectrum, are bundles of energy with no mass. However, x-rays and gamma rays have extremely high amounts of energy and can use that to remove electrons from atoms, unlike the other types of electromagnetic radiation.

Alpha particles and beta particles are also ionising radiation; however, they are not found on the electromagnetic spectrum. Instead, they are energetic charged particles.

Health effects of ionising radiation

What are the health effects of ionising radiation exposure and how does it affect human tissue?

Atomic structure

Atoms are the extremely small particles that are the basic building blocks of ordinary matter.


What is the difference between radiation and radioactivity?

Alpha particles

Alpha particles are relatively slow and heavy compared with other forms of nuclear radiation.

Beta particles

Beta particles have a mass which is half of one thousandth of the mass of a proton and carry a single negative charge.

Gamma radiation

Gamma rays are electromagnetic energy emitted by the nucleus of some radionuclides following radioactive decay.


X-rays are a form of electromagnetic radiation similar to radio waves, microwaves, visible light and gamma rays.

Other types of radioactive decay

Alpha, beta and gamma radiation are the most common types of radioactive decay but there are other ways that unstable atoms can become stable.

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