Rainbow at Dawn

January 17, 2004


Provided by: Stanley David Furdyna
Summary authors & editors: Stanley David Furdyna

While waiting in line for my breakfast McMuffin near Albutis, Pennsylvania in late November, I noticed this early morning double Rainbow. On this late autumn morning, rain showers were being ushered out by an approaching cold front. The Sun in the east and the clouds and rain in the west resulted in this colorful display. The time was approximately 7:30 AM (Eastern Standard Time). A primary rainbow is produced by one internal reflection of sunlight from a rain drop. However, the secondary rainbow arises from two internal reflections, and the rays exit the drop at an angle of about 50° (for red light), rather than about 42° as is the case for the red portion of a primary bow. Blue light from the secondary bow emerges at an even larger angle -- about 53° as opposed to about 41° for the primary bow. This effect produces a secondary rainbow that has its colors reversed compared to the primary bow. The secondary bow is faint on this photo -- it appears to the outside or left of the primary bow. Also notice the supernumerary bows just inside of the violet arch of the primary bow.

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