A torch beam lights up a person's hand because the hand is exposed to light, which is visible electromagnetic radiation. Exposing objects to beams of radiation is called irradiation. This term applies to all types of radiation, including radiation from the nuclei of atoms.
Irradiation from radioactive decay can damage living cells. However, it can be put to good use as well as being a hazard.
Contamination occurs if an object has a radioactive material introduced into it.
The two processes of irradiation and contamination are often confused. However they are very different and useful in their own right.
|Occurs when an object is exposed to a source of radiation outside the object||Occurs if the radioactive source is on or in the object|
|Does not cause the object to become radioactive||A contaminated object will be radioactive for as long as the source is on or in it|
|Can be blocked with suitable shielding||Once an object is contaminated, the radiation cannot be blocked|
|Stops as soon as the source is removed||It can be very difficult to remove all of the contamination|