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 ` A Little Bit About Rainbows`

 

A rainbow is an optical and meteorological phenomenon that causes a nearly continuous spectrum of light to appear in the sky when the Sun shines onto droplets of moisture in the Earth's atmosphere. It takes the form of a multicolored arc, with red on the outside and violet on the inside. Even though a rainbow spans a continuous spectrum of colors, traditionally the full sequence of colors is most commonly cited as red, orange, yellow, green, blue, indigo and violet. The rainbow effect can be observed whenever there are water drops in the air and sunlight shining from behind the observer at a low altitude or angle. The most spectacular rainbow displays when half of the sky is still dark with draining clouds and the observer is at a spot with clear sky overhead. The rainbow effect is also commonly seen near waterfalls or fountains. Rainbow fringes can sometimes be seen at the edges of backlit clouds and as vertical bands in distant rain or virga. The effect can also be artificially created by dispersing water droplets into the air during a sunny day. The rainbow's appearance is caused by dispersion of sunlight as it is refracted by (approximately spherical) raindrops. The light is first refracted as it enters the surface of the raindrop, reflected off the back of the drop, and again refracted as it leaves the drop. The overall effect is that the incoming light is reflected back over a wide range of angles, with the most intense light at an angle of about 40 -42 . This angle is independent of the size of the drop, but does depend a lot on its shape and refractive index. A rainbow does not actually exist at a location in the sky, but rather is an optical phenomenon whose apparent position depends on the observer's location. All raindrops refract and reflect the sunlight in the same way, but only the light from some raindrops reaches the observer's eye. These raindrops are perceived to constitute the rainbow by that observer. The position of a rainbow in the sky is always in the opposite direction of the Sun with respect to the observer, and the interior is always slightly brighter than the exterior. In Greek mythology, the rainbow was considered to be a path made by a messenger (Iris) between Earth and Heaven. In Chinese mythology, the rainbow was a slit in the sky sealed by Goddess Nuwa using stones of five different colours. In Hindu mythology, the rainbow is called Indradhanush, meaning the bow of Indra, the God of lightning and thunder. In Norse Mythology, a rainbow called the Bifrost Bridge connects the realms of Asgard and Midgard, homes of the gods and humans, respectively. The Irish leprechaun's secret hiding place for his crock of gold is usually said to be at the end of the rainbow (which is impossible to reach).

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Rose!