Double Rainbow with Supernumeraries over Bryce Canyon

A double rainbow is seen over Bryce Canyon just after a thunderstorm passed over. Although double rainbows are quite common, whats more interesting about this photo is the presence of several supernumeray rainbows just beneath the primary rainbow. These are slightly detached bands of pastel color and their existence is not easily explained by classic geometric optics. These alternating supernumerary rainbows are caused by interference between rays of light following slightly different paths with slightly varying lengths within the raindrops. Some light rays are in phase, reinforcing each other through constructive interference, creating a bright band, while others are out of phase, cancelling each other through destructive interference. Supernumerary rainbows are clearest when raindrops are very small and of uniform size. The existence of supernumerary rainbows was historically a first indication of the wave nature of light and first explained by Thomas Young in 1804.

Image Specifications:

     •  Instrument:  Canon EF 200mm f/2.8L @ f9.0
     •  Camera:  Canon 20Da
     •  Filters:  None
     •  Mount:  None
     •  Guiding:  None
     •  Time / Date :  4:30PM MST / September 8, 2007
     •  Location:  Bryce Canyon, Utah
     •  Weather:  Cloudy with passing storms, 75degF
     •  Primary Exposure :  1/320s, ISO 100
     •  Calibration Frames:  None
     •  Image Processing :  Photoshop Levels, Curves, Unsharp Mask