Beverly Carr., age 11, Meridian, Ida., for her question;

Why does a rainbow always have the same colors?

We are told that there are seven colors in the glimmering rainbow  but it is not easy for our eyes to separate them. Each colored band blends into the next with countless merging tones between them. Actually, the radiant rainbow contains all the colors Our eyes can see  except black and white which are not rated as true colors.

In a single rainbow, the red is at the top of the glimmering arch. The lower border is a ribbon of violet, which often loses itself in the grey blue of the rain cloud. Between the red and blue Our eyes See a Series Of blurry bands Which look like rain washed borders of assorted flowers. But the rainbow is the spectrum of white light, and its colors are always arranged in a definite order for a very good reason.

There are seyen basic colors in the spectrum with an endless variety of in between shades, where each basic color b1ends with the next. The basic colors are red, orange, yellow, green, blue, indigo and violet. The imaginary character, Roy G. Biv, was invented for you to remember the proper order of the spectrum colors of white light.

Each colored ray represents a wave length, which is a pulsing little hump of energy. All wave lengths pulse along at about 188,000 miles a second, but some are longer than others. The wave lengths of red rays are the longest, and they get shorter and shorter in order of the spectrum. The shortest are of violet.

    Each pulsing wave length is like a hill and dale, and it is measured from one crest to the next. You can imagine how small they are by comparing them to the thickness of one page of paper. This tiny distance is equal to about 130 red wave lengths and about 260 violet wave lengths.

Falling raindrops bend and scatter the wave lengths of light. The shorter ones have steeper sides than the longer ones, and hence the different wave lengths are bent at different angles. The colors of white light are separated in the order of the spectrum from the shortest to the longest. The longer red ones are bent least, and the red band of color is angled to our eyes from the top of the rainbow. The short Violet rays are bent most, and they take their place at the bottom of the orderly spectrum of rainbow colors.

Sometimes we see two rainbows in a double arch. The lower arch is the true or Primary rainbow, and its colors arc brighter. The secondary rainbow above it is a reflection of the primary rainbow. Its colors are in the proper Spectrum order, but they are reversed. The blue band is at the top, the red band at the bottom. When conditions are just right, We may see three, four or even five rainbows, one above another.