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Basically when you see a rainbow, what you are witnessing is the refraction of sunlight through water droplets. The colours occur because when sunlight passes through the droplets, it “divides” itself into a range of colours.

According to the National Center for Atmospheric Research
“the traditional rainbow is sunlight spread out into its spectrum of colors and diverted to the eye of the observer by water droplets”

“What makes the colors in the rainbow?
The traditional description of the rainbow is that it is made up of seven colors – red, orange, yellow, green, blue, indigo, and violet. Actually, the rainbow is a whole continuum of colors from red to violet and even beyond the colors that the eye can see.

The colors of the rainbow arise from two basic facts:

Sunlight is made up of the whole range of colors that the eye can detect. The range of sunlight colors, when combined, looks white to the eye. This property of sunlight was first demonstrated by Sir Isaac Newton in 1666.
Light of different colors is refracted by different amounts when it passes from one medium (air, for example) into another (water or glass, for example). ”

A shadow is defined by the Merriam-Webster Online dictionary in this context as “1 : partial darkness or obscurity within a part of space from which rays from a source of light are cut off by an interposed opaque body”

As the rainbows are essentially visual phenomena caused by sunlight and water droplets, rather than a physical object that can block light, hence it would not cast a shadow as defined above.

The website provided above has more detailed information regarding rainbows.

In addition, this reference has a fairly straightforward explanation, with diagrams:
Department of Atmospheric Sciences, University of Illinois

The books specifically on rainbows in our library are mainly children’s titles, here are a few:

The rainbow and you written by E.C. Krupp ; illustrated by Robin Rector Krupp
Call No.: J 551.56 KRU
Click here for item availability.

All the colors of the rainbow by Allan Fowler
Call No.: JP 551.56 FOW
Click here for item availability.

Answered by Jillian Lim, Librarian, Adult and Young People’s Services

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