Cloud Iridescence Over Switzerland
November 17, 2004
This very colorful iridescent cloud was photographed on September 25, 2004 at 10.45 a.m. (local time), near Lugano, Switzerland. Iridescence in clouds is caused by the process of diffraction, which is essentially the deflection of light around cloud droplets -- a result of the wave properties of light. Since iridescent clouds are simply detached coronae, they observed in patches or bands relatively close to the Sun, almost always closer than the 22 degree halo.