Question

what happens to cause this natural dispersion of sunlight

Answer 1

The cause of dispersion of light is that white light consists of seven different colours, and each colour has different angle of deviation. Therefore, on passing through the prism different colours deviate through different angles. Hence the seven colours of white light separates and form a spectrum. Out of seven colours, the red colour deviates the least, and hence the red colour is present at the top of the spectrum. On the other hand, the violet colour deviates most that is why violet colour is present at the lower end of the spectrum.

Answer 2

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The dispersion of light is the principle underlying in the formation of the rainbow. A rainbow is formed when white light is dispersed naturally. The rain drops act as dispersers while the Sunlight fall on them.