Why Is The Rainbow Curved?
About the Rainbow
The rainbow is the product of millions of reflections from millions of raindrops, each acting as a tiny prism.
Whenever Nature shows us the spectrum in the form of the rainbow, we see the order maintained, from violet on the inside of the bow to red on the outside. If there be a second bow outside the first, as sometimes happens, the same order persists, but the other way round -- red inside, violet outside.
One always sees a rainbow in the quarter of the sky away from the sun. That is, one must have one's back to the sun in order to behold it.
Rainbow is happening all over the sky, but we get reflections only from those drops in the right positions to reflect light to us.
What about the curve of the rainbow?
Why the rainbow is curved?
To make the reason for this clear, imagine a string to run from the eye to a raindrop, and from it to the sun. Imagine, too, an airman holding the string at the point where it bends and flying through space, keeping the string tight the while. He will describe part of a circle.
From near sea-level the bow is semi-circular. But as we go higher up more of the circle become visible. From a balloon or very high mountain a complete circle of colours -- one cannot in this instance speak of a bow -- is seen.