Ronnie Gantt, age 10, of Caycey S,C,, for his question:
Why is the rainbow curved?
The rainbow is always an arc, or part of a perfect circle. We say that it is an arc of 42 degrees because it is 42 degrees of an entire circle which has 360 degrees. In real life, the rainbow is a hazy blur of banded colors and. when there is only one bow, the outer band is always red. The reason it forms an arc is a problem in geometry with countless angles. If you find the explanation hard to grasp, dust swallow what you can and leave the rest for next year or the year after.
An angle is a corner with two straight sides, rather like a piece of pie. A big piece of pie has a wider angle than a small, piece of pie, The sides which form the angles in a rainbow are made of sunbeams. These sunbeams come from the sun which is low in the sky. They strike millions of raindrops falling from a cloud on the opposite side of the sky. When this happens, a white sunbeam is broken into a skein of rainbow colors. Each colored ray leaves the raindrop at a different angle and travels away in its own direction. Some of these colored rays reach your eye.
Only one of the colored rays from each falling raindrop can reach your eye and very strict laws of geometry say which one it shall be. This depends upon the angle at which the ray of colored light loaves the raindrop ‑ and the angle depends upon the wave length of this ray, Light travels in tiny waves or pulses, i4 wave length is like a little hill and dale and each colored ray travels on a different wave length. Imagine the thickness of a sheet of paper ‑ which is very thin indeed. The red rays make 130 waves in this short distances the blue rays make 260 waves in the same distance.
A clear liquid raindrop forces a sunbeam to bend and because of the different wave lengths, the colored rays bend at different angles.
The sunbeam turns around and fans out in a skein of colors. The blue rays with the longest wave lengths are bent most and make the smallest angles. The red rays with the longest wave lengths are bent least and make the widest angles.
These fans of colors are being sent from millions of falling raindrops in the cloud, all the angles of the same size arrange themselves along the arc of a circle, which means that all the angles of the same color form a curved band for your eye to see. The red rays, with their widest angles form the biggest curve, which is why a single rainbow is red on the outer rim. Though blurred, the other colors follow in smaller arcs in this order ‑ orange, yellow, green, blue, dark blue and violet.