Colour of objects

A material gets its colour as electrons absorb some wavelengths of light and reflect others. The colour an observer sees corresponds with the reflected wavelengths.

  • Three key factors affect the colour of an object:
    • The light source and what happens to the light on its journey towards an object.
    • What happens when light strikes a material or medium.
    • Factors related to an observer that affect the way they perceive things.

A material gets its colour as electrons absorb some wavelengths of light and reflect others. The colour an observer sees corresponds with the reflected wavelengths.

About chromophores
  • Things appear to have colour because they absorb some wavelengths of light and reflect others.
  • Chromophores are the part of molecules responsible for the absorption and reflection of light.
  • A chromophore is formed by a group of atoms within a molecule and the electrons that orbit their nuclei.
  • The colour produced by an opaque object corresponds with the wavelengths not absorbed during the interaction of light with the chromophores of the molecules that form its surface.
  • Whether different wavelengths of light are absorbed or reflected by a chromophore depends on whether there is an energy difference between orbiting electrons.
  • If the energy difference between the electrons of a chromophore falls within the range of the visible spectrum (2 to 2.75 electron volts) then it produces the colour seen by an observer.