rainbow is an optical phenomenon produced by illuminated droplets of water. Rainbows are caused by reflectionrefraction and dispersion of light in individual droplets and results in the appearance of an arc of spectral colours.

  • Rainbows can be produced by meteorological phenomena, waterfalls, lawn sprinklers and other things that create a fine mist of water.
  • A rainbow is formed from millions of individual raindrops each of which reflects and refracts a tiny image of the sun towards the observer.
  • It is the dispersion of light as refraction takes place that produces the rainbow colours seen by an observer.
  • If the sun is behind an observer then the rainbow will appear in front of them.
  • When a rainbow is produced by sunlight, the angles between the sun, each droplet and the observer determine which ones will form part of a rainbow and which colour each will produce.
  • Rainbows always form arcs around a centre point because each colour is at a different angle to an observer.
  • Seen from the air a rainbow can appear as a complete circle. It is only because the ground around the observer gets in the way that a rainbow produced by sunlight is reduced from a circle to a semi-circle or an arc.
  • The sky inside a rainbow is bright because raindrops direct light there too.
  • Rainbows caused by sunlight always appear in the section of sky directly opposite the sun.
  • and centred on a line from the sun to the observer’s eye.
  • When a single rainbow is observed then red will appear on the outside, followed by orange, yellow, green, blue, with violet on the inside.
  • When a double rainbow is observed then the second rainbow will be outside the first, it will be less intense, and the colours will be in the reverse order with violet on the outside.