Multiple Diffraction
February 09, 2005
Provided and copyright by: Reinhard Nitze
Summary authors & editors: Reinhard Nitze
This photo showing both a corona and cloud iridescence was taken in the late afternoon on April 18, 2004 from Barsinghausen, Germany. The corona (pastel rings around the blocked out Sun) is caused by pollen, perhaps from birch trees, while the cloud iridescence is due to tiny water droplets in the altocumulus cloud (altocumulus lenticularis). Both of these phenomena result from diffraction -- deflection of light by droplets and other minute particles. In essence, an iridescent cloud is a detached solar corona. Pollen coronas are a rather rare phenomenon. They most often occur during clear, warm and dry weather in the early spring, when the concentration of pollen in the air is greatest.
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