Physics

Radiation

Radiation is the emission of energy in the form of rays or waves travelling through space. Sunshine is the most common form of radiation. Sunshine consists of radiation in a number of different wavelengths. Ranging from the long wave infra-red to the short wave ultra violet (UV). It is the short waves of the electromagnetic spectrum that are most beneficial and cause the most harm.

Cosmic Rays	Gamma Rays	X-Rays	Ultra-Violet rays	Visible Light	Infra-red	Microwaves	Radio Waves

High Frequency

The

Electro-

Magnetic

Spectrum

Low Frequency

Remember: If a wave has a high frequency it has a short wavelength and if it has a low frequency it has a long wavelength.

The radiation form radioactive materials is invisible and has to be detected by the affects that it produces. The two methods of detection depend on the facts that (a) radiation exposes photographic materials and (b) it ionises gases.

Ionising of gases means that some of the atoms have an electron or two knocked out of their shells. These atoms are now positively charged ions. They can now conduct electricity. The Geiger counter is an electronic instrument that uses the ionisation of gases.

Uses of Radiation

	Killing Cancer cells - Although radiation is harmful to living cells cancer cells are more easily damaged by ionising radiation than healthy cells are. high doses directed at the cancer cells can kill with as little damage as possible to the living healthy cells.
	Sterilisation - bacteria are killed by large amounts of radiation. This is used to sterilise medical equipment.
	Tracers - radiation is feed into a liquid and then can be traced. In humans it is injected into the blood or can be inhaled to check the respiratory organs. This technique is used to check the brain, lungs, kidneys and bones are in functioning order.
	Agriculture - control of serious crop damage and to see in what amounts phosphorus is needed for healthy growth of plants.
	Food irradiation - Keep food fresher for longer and can kill any food-borne diseases. This does not mean that the food is then a radioactive source nor does it pass it on to humans.

So if radiation has all these benefits why is it so dangerous?

High doses of any kind of ionising radiation cause chemical and biological changes in human cells. These changes can bring about diseases such as skin, bone and lung cancer and leukemia. (Please note, however these cancers can be as a result from other causes)

The effect of radiation on Humans depends on the:

Type of radiation
Time exposure
Type of tissue irradiated

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