EM Spectrum


EM Spectrum

All EM waves travel at 300 000 000m/s (300 million) in a vacuum (space).


Visible light is absorbed by a surface and the surface's colour is reflected.


The colour passing through is visible, all other wavelengths of light are absorbed.

Black surfaces absorb and emit infared radiation the best and white absorb and emit infared radiation the worst.

All EM waves are transverse.

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Radio waves - Non-ionising

  • Generally safe
  • Used for communications ,radio, TV, satellite transmissions
  • Can travel through the atmosphere for long distances
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Microwaves - Non-ionising

  • Burning if concentrated
  • Used for communications satellites, telephones, heating water and food
  • Travel through the atmosphere
  • Specific frequency agitates water molecules causing them to vibrate and heat
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Infrared - Non-ionising

  • Burning if concentrated
  • Used in security lighting, remote control, heating
  • Heating energy is transferred by IR energy to other object causing them to gain heat energy
  • IR cameras can detect heat waves
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Visible light - Non-ionising

  • Burning / blindness if concentrated
  • Used for illumination, fibre optics and photography
  • Light rays act on retina allowing objects to be seen
  • Light can travel through optical fibres to carry information
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Ultraviolet - Ionising

  • Causes sunburn, skin cancer
  • Used for security marking, flourescent lighting, disinfecting water
  • Some materials absorb UV and re-emit this as visible light.
  • Energy effiecient lighting.
  • UV light kills micro-organisms
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X-rays - Ionising

  • Causes cell destruction, cell mutation and cancer
  • Observing internal structures
  • Airport security scanners
  • X-rays pass through soft tissue in the body
  • Penetrate different materials to a different extent so produce internal images
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Gamma rays - ionising

  • Causes cell destruction, cell mutation, cancer
  • Sterilizing, detection and treatment of cancers (medical imaging)
  • Kill living tissue and microbes
  • Injected gamma tracers pass through the body to produce images of internal organs
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Visible light Spectrum

Image result for visible light spectrum

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