Discovered in 1896 by the French scientist Henri Becquerel, radioactivity is a natural phenomenon found in our environment. While working on phosphorescence, the French physicist discovered that some substances such as uranium emit natural radiation, called ionising radiation. Substances that issue ionising radiation are radioactive.
There are several types of ionising radiation, including:
- alpha radiation (α);
- beta radiation (β);
- gamma radiation (γ);
Inversely, there is also non-ionising radiation such as low-frequency electro-magnetic fields (electrical devices), radio waves, microwaves and optical radiation such as infra-red and ultraviolet.