An arc of spectral color that appears in the sky when sunlight is refracted, internally reflected and dispersed by water droplets, typically seen opposite the sun during or after rain. The primary bow always shows red on the outer edge and violet on the inner edge, and a fainter secondary bow, with its colors reversed, sometimes appears further out where light reflects twice inside each droplet. Because a rainbow's position depends entirely on the angle between the sun, the observer and the droplets, no two people ever see exactly the same rainbow.
Facts
PeriodicityVisible only when sunlight from behind the observer strikes airborne water droplets and the sun's elevation is below about 42 degrees; the longest observed rainbow on record lasted 8 hours 58 minutes, seen over the Yangmingshan range of Taipei, Taiwan in November 2017. 1 ScaleA primary rainbow subtends an angular radius of about 42 degrees around the point opposite the sun; a secondary (double) rainbow, when present, appears about 10 degrees farther out with its colors reversed. 1 First DescribedThe classical Greek scholar Aristotle was the first to devote serious scientific attention to explaining the rainbow, and later analysis by scholars largely reacted to his account for centuries afterward. 1 Identification
Distinguishing AppearanceA multicoloured circular arc caused by refraction, internal reflection and dispersion of sunlight in water droplets, always appearing in the sky opposite the sun; a primary rainbow shows red on the outer edge and violet on the inner edge. 1 Sources
1. Rainbow (Wikipedia)
WikipediaWikipedia 'Rainbow', lead and Visibility sections
at lower latitudes near midday (specifically, when the sun's elevation exceeds 42 degrees) a rainbow will not be visible against the sky
Wikipedia 'Rainbow', lead section
The rainbow takes the form of a multicoloured circular arc.
Wikipedia 'Rainbow', Scientific history section
The classical Greek scholar Aristotle was first to devote serious attention to the rainbow.
Wikipedia 'Rainbow', lead section (scale sentence)
In a double rainbow, a second arc is seen about 10° outside the primary arc. Its colours are perceived to be in reverse order, with red on the lower side of the arc.
Wikipedia 'Rainbow', lead section (distinguishing-appearance sentence)
The rainbow takes the form of a multicoloured circular arc.
View the Source Reader Challenges (0)
No disputes yet. Spotted an error or a better source? Open the first one.
Sign in to dispute this or suggest a correction.