FOGBOW Sunlight shining through fog gives rise to a white bow. Fog drops are at least an order of size smaller than raindrops. Rather than splitting the colors into well-defined bands, the small drops create much broader bows that overlap and merge into a ghostlike arc. Only the lens-focusing effect of the drop's surface remains distinct, maintaining the high-intensity white bow. Credits: Photo: Courtesy of Christopher Michel on Wikimedia Commons, CC BY 2.0
Think You Know Rainbows? Look Again [Slide Show]
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CLASSIC RAINBOW A single-arc rainbow appears when sunlight reflects just once inside each of the many airborne droplets left by a rainstorm before it exits. A second, dimmer rainbow with inverted colors (top left) can appear above this primary rainbow if some of the incoming light is reflected twice before it escapes...
FOGBOW Sunlight shining through fog gives rise to a white bow. Fog drops are at least an order of size smaller than raindrops. Rather than splitting the colors into well-defined bands, the small drops create much broader bows that overlap and merge into a ghostlike arc...
WATERFALLS AND FOUNTAINS Rainbows form when sunlight interacts with water drops in the atmosphere. These drops do not have to be part of a rainstorm; rainbows can appear at the base of fountains and waterfalls, in ocean spray and in morning dew...
BLOOD RED BOW When the sun lies just on the horizon, its light has to travel through more of Earth's atmosphere than at any other time of the day before it reaches the falling drops from a rainstorm...
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SUPERNUMERARY ARCS Additional bands appear below the main arc of a rainbow when the rain shower contains drops that are all about the same size. These bands arise from interference of the light as it exits the drops...
DARK BAND The band of sky between two bows is always darker than the region inside the first and outside the second. This is due to the curvature of their droplets. Almost none of the light reflected by drops between the two bows reaches the observer, so this part of the sky appears darker...
LOW HANGER The position of a rainbow in the sky is largely determined by the sun's elevation. Near noon rainbows sit lower on the horizon than at any other time of the day.
Photo: Courtesy of Richard Webb on Wikimedia Commons, CC BY-SA 2.0..
360-DEGREE RAINBOW All rainbows would complete a full circle if the ground did not get in the way. If you can get to a high enough vantage point, you may be able to glimpse a rainbow in its full 360-degree splendor...
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