Rainbow

From Encyclopediak

Rain’bow”, a curved band of color often seen in the heavens during or after a rain or commonly seen in the mist over cataracts or falls. It is caused by the reflection and refraction of the sun’s rays when they strike the spher�ical drops of water at certain angles. The drops act like prisms and by refrac�tion separate the rays into the seven colors of the spectrum. A complete bow is made up of two bands of color. The inner and more distinct is called the pri�mary bow; it is formed by the rays strik~ mg the drops on the upper side, being refracted as they pass into the drop, striking the inner surface and being to�tally reflected to the lower side of the drop, where they are once more re�flccted as they emerge and so reach the eye of the observer. The red rays are at the outer part of the band, the violet at the inner, and the intermediate col�ors, arranged in order, lie between. In the secondary bow, which lies above, the colors are reversed and are less distinct; this is because this bow has been formed by the rays that strike the drops on the lower side, and the light rays have been twice totally reflected within the drop. Sometimes other bows appear within the primary how and overlapping the violet; these are called supernumerary bows and are seen only when the pn�mary bow is of unusual brightness. The center of the bows is always in a line from the sun through the eye of the ob�server. A bow known as a white rain�bow is occasionally seen by moonliflt. Its whiteness is due only to the faint�ness of the light, as all colors are less distinct by moonlight. As has been said, rainbows are also seen in mists over falls and are noticeable in escaping steam, and even sometimes in the dew on the grass, when the sun is at the right angle. See LIGHT, subhead Refraction of Light.