Rainbow and Supernumerary Bows Over Pilesgrove, New Jersey

January 19, 2011

Photographer: Lisa Gonnelli 
Summary Author: Lisa Gonnelli; Jim Foster

This photo shows an exceptional set of supernumerary bows beneath the gentle arch of a primary rainbow as observed from Pilesgrove, New Jersey on October 27, 2010. Note that the inside color of the primary bow is violet; whereas the outermost portion of the supernumeary bow is red. Three distinct supernumerary bands are clearly visible here. Supernumerary bows are caused not by refraction, as with the primary and secondary rainbows, but rather from diffraction of sunlight. The droplets that are responsible for these usually faint bows are much smaller than raindrops. While geometric optics explains the primary rainbow, wave theory of light is required to explain the formation of supernumerary bows. In essence, a ray of sunlight is bent ever so slightly after skirting the edge of a droplet, and as a consequence of constructive and destructive interference, this light is deflected over small angles by the myriad droplets. The more uniform in size the droplets are the more likely multiple supernumerary bows will be visible. Photo taken at about 3:30 p.m.

Photo details: Camera Maker: OLYMPUS IMAGING CORP.; Camera Model: E-500; Focal Length: 37.0mm; Aperture: f/6.3; Exposure Time: 0.0080 s (1/125); ISO equiv: 100; Exposure Bias: none; Metering Mode: Matrix; Exposure: Creative Program (based towards depth of field); White Balance: Auto; Light Source: Unknown; Flash Fired: No (Auto); Orientation: Normal; Color Space: sRGB.