Rainbow

A rainbow is an optical and meteorological phenomenon that causes a nearly continuous spectrum of light to appear in the sky when the sun shines onto falling rain. It is a multicoloured arc with red on the outside and violet on the inside. The full sequence of colours is most commonly cited as red, orange, yellow, green, blue, indigo, and violet, though it is important to note that this is an inconsistent list; all primary and secondary colors are present in some form, but only one tertiary. It is commonly thought that indigo was included due to the different religious connotations of the numbers six and seven at the time of Isaac Newton's work on light, despite its lack of scientific significance and the poor ability of humans to distinguish colors in the blue portion of the visual spectrum.

References

• Robert Greenler, Rainbows, Halos, and Glories, (1980) ISBN 0-521-38865-1
• David K. Lynch & William Livingston, "Color and Light in Nature", 2nd edition (2001) ISBN 0-521-77504-3
• M.G.J. Minnaert, "Light and Color in the Outdoors", 1995 ISBN 0-387-97935-2
• M. Minnaert, "The Nature of Light and Color in the Open Air", 1973 ISBN 0-486-20196-1
• Nussenzveig, H. Moyses, ?The Theory of the Rainbow,? Scientific American 236 (1977), 116