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Visibility of natural tertiary rainbows
1Mathematics and Science Division, United States Naval Academy, Annapolis, Maryland 21402, USA. raylee@usna.edu
Applied Optics
|October 22, 2011
Summary
Tertiary rainbows are extremely rare, often considered invisible due to glare. This study reveals they are visible under specific lighting and raindrop conditions, challenging previous assumptions about these rare optical phenomena.
Area of Science:
- Atmospheric optics
- Light scattering phenomena
Background:
- Naturally occurring tertiary rainbows are exceptionally rare.
- They are often presumed invisible due to sun glare and forward scattering by raindrops.
Purpose of the Study:
- To analyze the visibility of natural tertiary rainbows.
- To determine the conditions under which tertiary rainbows can be observed.
Main Methods:
- Utilized Lorenz-Mie theory for light scattering calculations.
- Employed the Debye series and a modified geometrical optics model.
- Incorporated interference and nonspherical raindrop effects.
Main Results:
- Calculated chromaticity gamuts, luminance contrasts, and color contrasts.
- Results indicate tertiary rainbows are visible under specific, unusual conditions.
- Visibility depends on unique lighting and raindrop size distributions.
Conclusions:
- Natural tertiary rainbows are not inherently invisible.
- Their visibility is contingent upon specific atmospheric and lighting parameters.
- This research provides a theoretical basis for observing these rare optical events.
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