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There is radioactivity all around us all the time
Some of this natural radioactivity comes from cosmic rays and rocks (especially granite) is very useful in medicine for treating some diseases
People are concerned about radioactive waste from nuclear power stations
The age of archaeological remains can be found using radioactivity
Food can be kept fresh for a long time using gamma radiation
Radioactivity can be dangerous and we must use it with care
The fallout from nuclear accidents or explosions is radioactive
The paths of underground rivers can be traced using radioactivity

You should be able to see from the list that radioactivity can affect our lives in many ways.
There has always been radioactivity around but it was not discovered until the end of the last century. A Frenchman named Henri Becquerel was doing some experiments with X rays when he noticed that some film that he put in a packet in a drawer under a pieced of uranium ore had become fogged. This was strange because no light could get in and he therefore decided that the uranium was giving out some sort or radiation that could go through the paper of the packet.

Marie and Pierre Curie later followed up his discovery and called the radiation RADIOACTIVITY.

Some years later physicists realised that radioactivity was due to an in-balance of neutrons and protons in the nucleus of an atom. It was not that there were more neutrons than protons it was just that the numbers of each were not ‘right’ and the nucleus became unstable.

It was discovered that there were three types of radiation and the Curies named them alpha, beta and gamma. Later experiments revealed that the radiations were ionising and were emitted randomly from unstable nuclei.

The Curies extracted a much more radioactive material from the uranium ore, they called this new substance RADIUM. It took many tons of ore to give a few milligrams of radium.
They suggested that the radioactivity:
(a) was not affected by heat, pressure or chemical reaction
(b) did not seem to get any weaker as time passed in the way that a hot object cools down
(c) appeared to have no effect on them.

Dangers of radioactivity

Unfortunately they were wrong about the last two points and in fact Marie Curie died of leukemia due to the effect of the radiation on her blood. We now know that large amounts of radioactivity can produce burns on the skin, cause blindness and even death. People can become sterile, develop cancerous growths and even their unborn children can be affected as a result of being exposed to high doses of radiation. It is therefore important that we always obey the safety rules when using radioactivity.


Whenever radioactivity is being used there is a notice with this symbol on it to warn people. There are certain rules which you should always obey when using radioactivity.

1. If you are under 16 DO NOT USE IT AT ALL
2. NEVER touch a source with your hands
3. NEVER point a source towards anyone, including yourself
4. ALWAYS put the source back in its proper place after you have used it
5. ALWAYS keep the sources LOCKED away
6. ALWAYS keep as FAR AWAY from a source as possible
7. NEVER open a sealed radioactive source
8. REPORT any accidents immediately


The units for radioative decay are the Becquerel (Bq). One Becquerel is one decay per second. 1 kBq is one thousand decays per second.

This means that an alpha source with an activity of 100 kBq emits 100 000 alpha particles per second. If you think that this is a very large number remember that 1 g of radium will contain aver one million million million atoms.


© Keith Gibbs 2020