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Electromagnetic Waves.

Extracts from this document...

Introduction

Electromagnetic Waves

- Radio Waves.

Radio waves are used for broadcasting radio and TV programmes. The transmitted information may be analogue or digital and uses a radio wave as a carrier.

Very long wavelength radio waves can travel around the Earth despite its curvature, diffracting around the Earth's surface. These are sometimes called ground waves.

Medium wavelength radio waves are reflected from an electrically charged region of the Earth's atmosphere called the ionosphere. These waves are sometimes called sky waves and can also be sent from one part of the planet to another.

Shorter wavelength radio waves pass straight through the atmosphere and cannot be used to send information around the Earth's curvature. These waves are sometimes called space waves
and

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Middle

Infra-red waves (often called infra-red radiation) are easily absorbed by materials. The energy of the wave causes the material to get hot. We usually think of infra-red radiation as heat.

Ordinary ovens, grills and toasters use infra-red radiation to cook food
(ovens may also cook by
convection).

Infra-red waves can transmit information through the air to operate TV's and VCR's by remote control. Information can also be sent through optical fibres.

Intense infra-red radiation will damage or kill living cells (such as skin cells) by burning them.

- Ultraviolet.

Ultraviolet waves are often called ultraviolet light or ultraviolet radiation.

Some materials will absorb (take in) the energy from ultraviolet waves and emit (give out) the energy as visible light. These materials are called fluorescent and are used for fluorescent lighting (strip lighting)

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Conclusion

High intensity X-rays will kill living cells.

- Gamma rays.

Electromagnetic waves with a wavelength shorter than X-rays are called gamma rays or gamma radiation (not gamma waves). Gamma rays may be emitted from radioactive materials.

Low intensity gamma radiation can damage living cells and cause cancer.

High intensity gamma radiation will kill cells. It is used in a technique called radiotherapy to treat cancer by targeting the cancer cells with a beam of radiation and then rotating the source of the beam.

The normal cells receive a lower dose of gamma radiation than the cancer cells, where all the rays meet. Radiotherapy aims to kill the cancer cells while doing as little damage as possible to healthy normal cells.

Gamma radiation is used to kill micro-organisms, which is called sterilising. It is used to sterilise food and hospital equipment such as surgical instruments.

...read more.

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