Larry Kyte, age 13, of Burbank, S.D., for his questions
What is color?
Color is the result of a complicated collision and a collision cannot occur unless at least one of the parties is traveling. The traveler here is light, the fastest of all speeders. Whether it is a sunbeam or the pale beam from a candle, light whips along at about 186,000 miles a second. Light itself is one of the many forms of energy in the universe. This is a fact or phenomenon we just have to accept. We can study the nature of light from the way it behaves and color, perhaps, tells us more than anything else about it.
Most of our light, of course, comes from the sun across some 93 million miles of empty space. It is part of the radiant' energy poured forth by that glorious star day and night in all directions. The journey to the earth takes about eight minutes and on the way the speeding light meets no obstacles. Out in space it is white or colorless light. When it collides with the myriads of different surfaces on the face of the earth, this colorless light reveals the countless colors of the rainbow.
Obviously, then, these radiant colors must have been somehow hidden in the white light of outer space. When it strikes a surface, something must happen to reveal them. We can only explain this by the nature of white light itself. First, it fans out from its source in straight lines in all directions. Second, it travels out in tiny pulses of energy* Each of these pulses is called a wave length and has a trough and a crest.
There are many different wave lengths in a beam of white light. At the normal speed of light, all these wave lengths are blended together.
We can think of each wave length as a thread and a beam of white light as being made of many threads. When a sunbeam strikes a surface, the skein of threads is broken apart. Some are absorbed by the object. The rest are reflected back for our eyes to see. And we see them as colors.
The basis colors of the spectrum are red, orange, yellow, green, blue, indigo and violet. However, there are countless halftones and tinges between the basic colors. The red rays have the longest wave length, orange have shorter wave lengths and so on down to the violets which have the shortest wave lengths. In the distance equal to the thickness of a sheet of paper, red rays have about 130 wave lengths and violet have about 260.
When a beam of white light strikes a red rose, all the orange, green and blue rays are absorbed. The red rays are bounced back for our eyes to see. When a sunbeam falls upon the wing of a bluebird, all the red, orange, yellow and green rays are absorbed and the blues are reflected back. When the sun shines on a piece of polished ebony, all the rays are absorbed and none are reflected back. When a sunbeam strikes a calla lily, none of the rays are absorbed and the light is reflected back in its natural whiteness.