White light

White light is the name given to visible light that contains all wavelengths of the visible spectrum at equal intensities.

  • The sun emits white light because sunlight contains equal amounts of all of the wavelengths of the visible spectrum.
  • As light travels through a vacuum or a medium it is described as white light if it contains all the wavelengths of visible light.
  • As light travels through the air it is invisible to our eyes.
  • The term white light has two meanings. It can refer to:
    •  A mixture of all the wavelengths of visible light travelling through space without thinking about its observation.
    • What an observer sees when all the colours that make up the visible spectrum strike a white or neutral coloured surface.
  • The human eye also sees white when the wavelengths of light corresponding with the three primary colours red, green and blue (RGB) are projected onto a neutrally coloured surface.
  • Light is only visible as it is emitted by an object such as an electrical filament or when it strikes an object.
  • White light appears coloured when some wavelengths of light are reflected by the surface of an object but others are absorbed.
  • Artificial light sources typically emit light with an uneven distribution of wavelengths or intensities.
  • Whilst there is no single, unique specification of “white light”, there is indeed a unique specification of “white object”, or, more specifically, “white surface”.
  • White is the lightest possible colour.
  • White is an achromatic colour, meaning a colour without hue.