Question

Why Rainbow is circular in shape?

Answer 1

Rainbows always appear round because they are formed at a constant angle around the anti solar point (the shadow of your head). The shape of something described by an arc a constant distance away from a point is a circle, which is called round.

http://optics.kulgun.net/Rainbow/rainbow-faq.shtml#a13

http://www.math.ubc.ca/~cass/courses/m309-03a/m309-projects/endersby/Antisolarpoint.html

Answer 2

Rainbow, arch of light exhibiting the spectrum colors in their order, caused by drops of water falling through the air. It is seen usually in the sky opposite to the sun at the close of a shower and also in the spray of waterfalls. In the brightest or primary bow, often the only one seen, the colors are arranged with the red outside. Above the perfect bow is a secondary bow, in which the colors are arranged in reverse order; this bow is dimmer, because of a double reflection within the drops.

When the sunlight enters a raindrop it is refracted, or bent, by and reflected from the drop in such a way that the light appears as a spectrum of colors. The colors can be seen, however, only when the angle of reflection between the sun, the drop of water, and the observer's line of vision is between 40° and 42°.

When the sun is low in the sky the rainbow appears relatively high; as the sun rises higher, the rainbow appears lower in the sky, maintaining the critical 40°- to 42°-angle. When the sun is more than 42° above the horizon no rainbow can be seen because the required angle passes over the head of the observer.

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(plural rain·bow curves)
noun
good curveball: in baseball, a curveball with an exceptionally great arc

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##### rain·bow [ráyn b]
noun (plural rain·bows)
1. multicolored arc in sky: an arc of light separated into bands of color that appears when the Sun's rays are refracted and reflected by drops of mist or rain.
The colors of the rainbow are conventionally said to be red, orange, yellow, green, blue, indigo, and violet.
2. arc of bands of color: a multicolored arc similar to a rainbow
3. bright multicolored sight: an arrangement, display, or sight containing many bright colors or bright multicolored objects
the rainbow of colors on an artist's palette

4. false hope: a goal, hope, or ideal that is unlikely to be achieved or realized
5. varied assortment: a wide range or varied assortment of things, usually coexisting without clashing


adjective
1. having varied colors: having the colors of the rainbow or colors as varied as those of a rainbow
2. made of many different things: comprising a wide variety of types or elements, especially made up of people of different ethnic groups or from a variety of minority groups
a rainbow coalition




The Rainbow, a novel (1915) by British writer D. H. Lawrence.
Set in the English Midlands between 1840 and 1905, it describes the impact of contemporary social developments on the lifestyles and attitudes of succeeding generations of a provincial family, the Brangwens. The latter part of the book focuses on Ursula, the family's first independent woman, whose story is continued in a subsequent novel Women in Love (1920). ####