We are used to see­ing rainbows on rainy days, but the phe­nom­e­non oc­curs any­where in the pres­ence of wa­ter drops and light. De­pend­ing on the size of the drops, the light source, and the ob­server’s po­si­tion, the rain­bow might seem dif­fer­ent, although the pr

Science Illustrated - - NATURE/ RAINBOW -

MOONBOW: Rainbows are most fre­quently as­so­ci­ated with sun­light, but bright moon­light can also cause rainbows. How­ever, the colours are weak or nonex­is­tent, as our colour vi­sion is poor at night. The moonbow will hence very often seem whitish.

FOG BOW: Fog con­sists of wa­ter drops that are so small that in­di­vid­ual colours will be dis­persed and mixed to such an ex­tent that a wide, whitish rain­bow re­sults. So, this rain­bow will not al­ways be as­so­ci­ated with or­di­nary rainbows.

SUPERNUMERARY BOWS: On the in­side of the pri­mary rain­bow, you can very rarely ob­serve a se­ries of ex­tra arcs that do not form in the same way as the rain­bow it­self. These arcs are due to the fact that the light beams in a rain­drop can in­ten­sify or weaken each other (in­ter­fer­ence), and to make them vis­i­ble, it is nec­es­sary that the rain­drops be very sim­i­lar in size.

RAINBOWS IN WATERFALLS: A rain­bow is often pro­duced in the drops from the tur­bu­lent wa­ter vol­umes of a wa­ter­fall. There, you might see the en­tire cir­cu­lar rain­bow, if you are above the wa­ter­fall, look­ing down at the wa­ter drops.

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