When the atmosphere becomes loaded with particles, only the longest red wavelengths are able to penetrate the atmosphere, so we see a red Sun.

Question

Quizplus · Accepted Answer

When the atmosphere is loaded with particles, such as during a dust storm or after a volcanic eruption, shorter wavelengths of light (blue, green) are scattered out, leaving the longer red wavelengths to penetrate through, making the Sun appear red.

When the Atmosphere Becomes Loaded with Particles, Only the Longest