When discussing light,  a spectrum is a linear scale of spectral colours organised by wavelength.

  • A visible spectrum of colours is produced naturally when light is refracted by a prism or by raindrops.
  • The plural of spectrum is spectra.
  • The continuous distribution of colours in a spectrum is a result of the fact that visible light consists of a range of wavelengths, rather than distinct, separate colours.
  • A diagram of spectral colours is usually presented in the form of a spectrum, a linear band organised by wavelength with red at one end and violet at the other.
  • Spectra are often shown in an elongated form so that as many different gradations of colour can be seen as possible.
  • The process of separating light into its constituent colours is called dispersion.