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When does the green flash phenomenon occur?

On rare occasions, the final portion of a setting sun appears bright green. This "green flash," as it is known, is due to both refraction (bending) and scattering (reflection in every direction) of sunlight in the atmosphere.

The different color components of sunlight, each having a different wavelength, are refracted to different degrees as sunlight passes through the Earth's atmosphere. Red light, which has the longest wavelength, is bent the least, and violet light, which has the shortest wavelength, is bent the most. In between these two extremes are (from longest to shortest wavelength): orange, yellow, green, blue, and indigo.

As the sun sets over the horizon, yellow, orange, and red (the colors bent the least) are the first wavelengths of light to disappear. However, they are usually the only colors of a setting sun that we see. This is because the...

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