Rev. Notes > IGCSE > Light Previous Topic Light Next Topic Topics
 Nature of light Important features of light Reflection of light Use of mirror (Periscope) Refraction of light Refractive index Critical angle Total internal reflection Use of prism (Periscope) Fiber-optics Convex lens Behavior of standard rays after passing through convex lens Image formed by convex lens Nature and position of image produced by convex lens Principle of camera Dispersion of light Newton's experiment for dispersion of light Improvement in Newton's experiment for dispersion of light Recombination of colors Rainbow Reflection through plane mirror Image through plane mirror

## Rainbow

The rainbow is a natural phenomenon sometimes seen after a rain. In the seventeenth century a French mathematician Rene Descartes gave the idea that rainbow is produced by the dispersin of light. According the Rene, after the rain showers, a number of droplets of water remain suspended high up in the air. When sun light falls on theses water droplets, it gets splitted, as each drop acts like a prism. So each ray of light after passing through the drop suffers refaction and total internal reflection. The violet colour is refractetd the most and the red colour, at least. Thus the red ray which emerges from each droplet makes greater angle with the horizontal than the violet ray. Simiillarly other coloured rays emerge at different angles to the horizontal. The droplets which are at the same angle from the observer will produce the same colour. Consequently an area of coloured bands called the rainbow appear in teh sky opposite to the sun as shown in the figure below.

The colour in the rainbow are distributed in such a way that violet lies on the inside of the bow, while the red light outside of the bow.

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