Light — Why Does a Rainbow Have Seven Colours?
We learnt in school that light travels in straight lines, that it can be reflected and refracted, and that white light contains seven colours.
But what exactly is light?
Light is a form of electromagnetic radiation. The small portion that our eyes can detect is called visible light.
What we call white light is actually a mixture of different wavelengths. When sunlight passes through a glass prism, the different wavelengths bend by slightly different amounts and spread out into a spectrum:
Violet → Indigo → Blue → Green → Yellow → Orange → Red
This is called dispersion.
A rainbow is nature's own prism. When sunlight enters raindrops, it is refracted, reflected inside the drop, and refracted again as it emerges. The different colours separate, producing the familiar arc.
And there is a beautiful detail we often forget:
Red light bends the least; violet bends the most.
That is why the colours appear in a particular order.
Light also gives us colour itself. An object appears green, for example, because it reflects more green light towards our eyes while absorbing much of the other visible light.
So when we look at a rainbow, we are not seeing seven different kinds of light suddenly created in the sky.
We are seeing the hidden colours that were already present in white sunlight, separated and revealed by millions of tiny drops of water.
Perhaps that is the magic of light:
It doesn't merely help us see the world—it reveals what was hidden within it.
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