Questions
about Rainbows
Questions
about Rainbows
People
have been asking questions about rainbows since the beginning of time. One question
frequently asked is, how far away is that rainbow? That is a tough one. How far
away are the raindrops that produce it? It is hard to judge how far away a rain
cloud is; especially if it's moving. The rainbow's distance extends from the nearest
to the farthest raindrops that contribute any part of the colored light. The closest
of these raindrops may be miles away. In the case of water spray from a lawn sprinkler
in which a rainbow appears, you can reach right in and "touch it"....or
so it seems. Many questions are unique to one's cultural history. Where is that
pot of gold? That is a good question too.
The
idea that a pot of gold can be found at the rainbow's end originated somewhere
in old Europe. In Silesia, an obscure area of eastern Europe, it was said that
the angels put the gold there and that only a nude man could obtain the prize.
Hmm.....
Can
you go under a rainbow's arch and come out the other side? Not according to
the laws of physics. A rainbow is all light and water. It is always in front
of you while your back is to the sun. However, there is an old European belief
that anyone passing beneath the rainbow would be transformed, man into woman,
woman into man! Hmm....
Well, that would be less painful than going to a surgeon.
Do two people ever see the same rainbow? No. As the eyes of two people cannot
occupy the same place in space at the same time, each observer sees a different
rainbow. Why? Well, because the raindrops are constantly in motion so its appearance
is always changing. Each time you see a rainbow, it is unique in its own spectacular
way! Many people consider rainbows to be an omen of some kind. It is an ancient
desire rooted in our cultural mythologies.
The
legends of many cultures see the rainbow as a kind of bridge between heaven
and earth. One of the most beautiful sights in nature, the rainbow has become
in western culture a symbol of renewed hope; something lucky to look upon. To
Iranian Moslems, even the brilliance of the colors in a rainbow have significance.
A prominent green means abundance, red means war, and yellow brings death. The
Arawak Indians of South America recognize the rainbow as a fortunate sign if
it seen over the ocean, while tribes in northeastern Siberia see it as the tongue
of the sun. The North American Catawba Indians of the Southeast and the Tlingit
of the Northwest both regard it as the bridge between the living and the dead.
When
light and water meet in the sky on a summer's day, for a few moments, a rainbow
will appear. Such a beautiful sight! This phenomena of the atmosphere appears
during or immediately following local showers, when the sun is shining and the
air contains raindrops. A rainbow can best be seen with polarized sunglasses.
We cannot follow the arc of a rainbow down below the horizon, because we cannot
see those droplets in the air below the horizon. But the higher we are above the
ground, the more of the rainbow circle we would see. That is why, from an airplane
in flight, a rainbow will appear as a complete circle with the shadow of the aitplane
in the center.
The
bow is divided into bands displaying the different colors of the spectrum and
is formed by the refraction and reflection of the sun's rays in drops of rain.
Reflection is simply the return of light waves from the raindrop's surface.
Light which appears to be white, is really made up of a mixture of red, orange,
yellow, green, blue, and violet light.
When
a shaft of sunlight enters a drop of water, a part of it does not pass directly
through but is reflected from the inner surface and emerges from the side from
which it entered. Moreover, it is refracted both on entering and leaving the
water drop. This process, repeated in the same manner for an immense number
of drops, produces the primary rainbow, which appears in front
of the observer, who has his back to the sun. It has the red band on the outer
edge which are long light waves and the blue-to-violet on the inner edge which
are short light waves.
Another
larger bow is often seem outside the primary rainbow and parallel to it. This
secondary rainbow is produced in a similar way, but the sun's
light is reflected twice before emerging from the raindrop. For this reason,
the color sequence is reversed; red is on the inside edge. And because there
is a loss of light with each reflection, it is not as bright as the primary
rainbow. The region between the two bows is comparatively dark, for it lacks
entirely both the once and the twice reflected rays. There is theoretical evidence
for a tertiary rainbow , but it would be so faint as to be rarely
seen in nature.