Parts of the electromagnetic spectrum

Source, detection and application

  • Electromagnetic waves carry energy. The waves consist of transverse vibrations in electrical and magnetic fields, not vibrating particles.
  • Electromagnetic waves do not need matter to travel through - they can travel through empty space (a vacuum).
  • In a vacuum, all electromagnetic waves travel at 3 \times 10^{8}m\,s^{-1} - the fastest speed possible.
  • When electromagnetic waves travel through matter (for example, light passing through air or glass), they travel a bit slower than this but rarely less than half as fast as in a vacuum. The value for light travelling through a glass optical fibre, for example, is taken as 2 \times 10^{8}m\,s^{-1}.

The table below demonstrates the electromagnetic spectrum.

The electromagnetic spectrum
Type of waveTypical sourceExample of detectorApproximate wavelengthTypical usersDangers of over exposure
Radio: LW, MW and VHFelectronic circuitsaerial1km, 100m and 1mcommunications, radio, TVsafe (unless very concentrated)
Microwaveselectronic circuitsaerial1cm (10 ^{-2}m)communications satellites, telephony, heating water and foodburning, if concentrated
Infra red (IR)electronic devices, warm objects, sunelectronic detectors, heat-sensitive papers, black-bulb thermometer0.1mm (10 ^{-4}m)detector in security lighting, remote controls (e.g. TV)burning, if concentrated
Light; Red, Orange, Yellow, Green, Blue, Indigo, Violetelectronic devices (eg LED), suneye, photographic film, electronic components (eg LDR)0.001mm (10 ^{-6}m)seeing, photography, communication (eg in optical fibres), laser surgeryburning, blindness if concentrated
Ultraviolet (UV)sun, gas discharge, lampscauses fluorescence (glowing) in some objects, film0.00001mm (10 ^{-8}m)sun-tan lamp, making ions, making vitamin D, killing bacteria in water treatment plantssunburn, skin cancer, retinal damage
X-raysvery fast electrons hitting a metal targetphotographic film 10^{-10}mimaging breaks/defects in bones, hidden devicescell destruction, cell mutation, cancer
Gamma rays ( \gamma)radioactive nuclei decayingphotographic film, GM tube 10^{-12}mmedical tracers, killing cancerous cells, sterilisation of surgical equipmentcell destruction, cell mutation, cancer
Chart showing types of electromagnetic waves from radio to gamma rays, with visible spectrum illustrated.Chart showing types of electromagnetic waves

The electromagnetic spectrum ranges from long wavelength, low frequency waves (like radio waves which can be used for communication) to short wavelength, high frequency waves (like gamma rays which can be used for medical treatment).

In the electromagnetic spectrum, waves with higher frequency have greater energy than lower frequency waves.