Supernumerary Rainbow Over Modica, Italy

May 23, 2022


Photographer: Salvatore Cerruto

Summary Authors: Salvatore Cerruto; Cadan Cummings

During the afternoon of February 15, 2022, I was lucky enough to see a supernumerary rainbow in the sky over Modica, Sicily, Italy. These unique rainbow arcs are visible below the primary rainbow and are produced when incoming sunlight is diffracted through very small raindrops. Resulting from the diffraction process are regions of light wave interference where the colorful band are from constructive interference and the colorless gaps are from destructive interference.  

Supernumerary rainbows can be identified by several colored fringes- ranging from indigo to green- visible below the rainbow that also appear like the rainbow is repeating itself. To show the optical phenomenon in greater detail, I enlarged the part that had the supernumerary arcs and saturated it a little to highlight the features and colors. This specific composite image is a panorama composed of eight vertical shots taken using a Nikon DSLR camera with a 35mm lens.

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