|
Rainbows have always carried with them an aura of mystery and legend. Ancient Indian tribes across North America believed that a rainbow was the bridge between life and death. The Romans saw rainbows as a positive sign from their sun god. And a popular Irish legend says that the wee folk regularly leave pots of gold at the ends of a rainbows - the only trick to carting off that gold is getting to the end of a rainbow before it fades into memory. To date no human has had much luck fulfilling this elusive quest -- but not for lack of trying.
In reality there is nothing mythical, mystical, or even mysterious about rainbows. Many of us consider these multi-coloured arcs that appear in the eastern horizon after late afternoon rainstorms as beautiful and sometimes genuinely breathtaking gifts of nature. Yet the creation of a rainbow does actually follow various laws of physics that a scientist named Descartes began seriously investigating as far back as the 17th century. The formula involves variables like refraction and reflection of light, prisms, colour spectrums, antisolar points, and various other complicated-sounding words. But in reality, the formation of a rainbow is a rather simple science as long as all the variables are present at the moment of its creation.
Light is comprised of a series of colours: red, orange, yellow, green, blue, indigo and violet, not to mention other light, like ultraviolet, which is not as easily detected by the human eye. Light also has varying wavelengths. The longest wavelengths are visible to the human eye as the colour red, the shortest wavelength the colour violet, with a short list of other colours in between. When light passes through anything it will bend, or become refracted light. No two objects have the same refractive index. When light passes through an object like the ornamental crystals many people have hanging in their windows, each colour created will bend according to its corresponding wavelength and then spread to form rainbow colours on an opposite wall.
The same process occurs when the sun peeks out from behind the clouds during or right after a rainstorm. Raindrops must still be present in the atmosphere to create a rainbow. Think of a each single raindrop as a tiny prism or crystal. As the sun’s rays catch and shine through the droplets and the light refracts, or bends, this highly concentrated light once again breaks up into its various wavelengths and then goes on to create a rainbow. The colours of a rainbow always appear in the same order, beginning at the outer edge: red, orange, yellow, green, blue and violet. Sometimes the light reflects twice off the inside of a raindrop, creating a second rainbow just above the first. But when this happens the colours will appear in the reverse order, red on the inside, and so on. The colours of a secondary rainbow are usually never as bright as those of the primary rainbow either.
Rain showers and thunderstorms are not the only time rainbows occur. They may be observed in banks of fog or mist,in the spray that billows up from waterfalls or that’s created by lawn sprinklers or in any instance where light reflects through water or an object like a glass or a crystal. To see a rainbow in such an instance depends mostly on where the observer is standing. The light from the full moon can even create rainbows on the odd occasion, although these “lunary rainbows” are not seen nearly as often as those created by light from the sun.
Despite the science involved in the formation of rainbows, many of us may just prefer to keep these colourful arcs in an a simpler and ages-old context -- that of mystery and beauty -- and overflowing pots of gold guarded by sly and laughing leprechauns.
|
| |
