The Electromagnetic Spectrum

Different parts of the electromegnetic spectrum & other details

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  • Created by: Rachel
  • Created on: 08-04-09 09:29

Electromagnetic Waves

  • Consist of self-sustaining electric and magnetic fields
  • Light can be pictured as a combination of transverse electric and magnetic waves moving through space
  • Light waves are the result of electrons moving within atoms- an oscillating chrage which sets up an electric field and therefore a magnetic field
  • Radio waves are created by electrons moving in wires
  • EM waves travel through a vacuum at 3 X 10^8 ms-1
  • They are part of big "family" of waves with varying wavelengths
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Radio Waves

  • Highest frequency, longest wavelength
  • Used in communications
  • You can easily generate radio waves of a particular frequency using an alternating current and an aerial
  • Will not interfere with waves of another frequency- therefore many radio stations can broadcast in one area
  • The Ionosphere, an electrically charged layer in the atmosphere, reflects and refracts radio waves
  • Waves would be lost by the curvature of the earth but this prevents this from happening- reflected back down. This is used in the long distance broadcasting of radio signals.
  • But it means radio communications with satellites are not possible with the frequencies affected
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Microwaves

  • Higher freq, shorter wavelength that radio waves
  • Used for communications with satellites as they are not reflected by the ionosphere
  • Shorter wavelength so shorter aerial needed for transmitting/receiving
  • Ideal for mobile phones and other handheld communication devices
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Infrared

  • Higher freq, shorter wavelength than microwaves
  • Travels through glass in a very simlar way to light
  • Total internal reflection is used to carry it along optic fibres
  • Used for wire communications in this way to increase the range of frequencies used (alongside visible light) and therefore maximise the amount of information that can be transmitted at one time
  • Heat radiation is also carried primarily by infrared rays
  • Toasters and grills sue infrared to cook food
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Visible light

  • Wavelength 400nm-700nm
  • Very small section of the spectrum
  • Apart from a large range of radio waves, only wavelengths that naturally occurs at the surface of the earth
  • Sine birds and insects can also see in a range of UV wavelengths
  • Gives them richer, more detailed vision
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Ultraviolet

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