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Dewbow on a spiderweb

A dewbow is an optical effect, similar to a rainbow where the dewdrops reflect and disperse sunlight, producing all the colours in the visible spectrum.[1][2]


Although rare, dewbows are most common in autumn, when dewdrops form on a dense network of spiderwebs (or rarely on walls, grasses and other vegetation[3]), where the dew hanging on the webs acts like rain, and diffracts the light. [2]


A dewbow is centred on the antisolar point but as the dew is on a horizontal plane, the bow is not a circular arc, but often elliptical or an open arc shape in a parabola or hyperbola.[1] The precise shape of the bow depends on the elevation of the sunlight, and any slope present on the dew covered ground.[2]

See also[edit]


  1. ^ a b Boyle, Kevin. "Dewbow". Retrieved 2009-07-19. 
  2. ^ a b c Dunlop, Storm (2009). Weather. Collins. p. 151. ISBN 978-0-00-784141-7. 
  3. ^ Edens, Harald. "Dew bow". Retrieved 2009-07-19.