An LED (Light-emitting-diode) is an electroluminescent light source. It produces light by passing an electrical charge across the junction of a semiconductor.

Multi-colour LED’s typically contain three separate diodes that mix red, green and blue wavelengths to produce a full range of colours.

  • LED’s don’t produce white light in the same way that incandescent lamps do.
  • One LED cannot produce the full range of colours that sunlight or incandescent light produces.
  • A LED typically emits a single colour of light which is composed of a very narrow range of wavelengths.
  • However LED’s emitting the three primary colours of red, green and blue light can be combined to produce white light.
  • By changing the relative intensity of the primary colours, a multi-colour LED produces an extremely wide range of colours.
  • An LED light source is often used to demonstrate the effect of projecting primary coloured lights onto a dark surface because they emit light in very narrow bands of wavelengths. The peak wavelength for the selected lights might typically be red = 625 nanometres, green = 500 nm, blue = 440 nm.