The amplitude of a wave is a measurement of the distance from the top of a crest through the centre line  (the still position, zero-point, mid-point) to the bottom of a trough.

In the case of an electromagnetic wave, amplitude corresponds with the intensity of light and the brightness of colour perceived by an observer.

  • When the amplitude of an electromagnetic wave of a specific wavelength increases so does the overall distance between the peak and the trough of the wave.
  • The measurement taken between the topmost point on a wave (the peak) and the centre line of the wave is called peak amplitude.
  • Amplitude is measured in metres (m).
  • The greater the amplitude of a wave, the more energy it carries.
  • When amplitude increases so does the perceived vividness of a colour.
  • Whilst the perceived brightness of a colour depends on the amplitude of a light wave, brightness is also somewhat influenced by wavelength. So for example yellows tend to look brighter than reds or blues.