Why the sun appears red at sunrise and sunset?
At the time of sunrise and sunset, when the sun is near the horizon, the sunlight travels the greatest distance through the atmosphere to reach us. During this, most of the shorter wavelengths present in it are scattered away from our line of sight. So, the light reaching us directly from the rising sun or setting sun consists mainly of longer wavelength red color due to which the sun appears red. Thus, at sunrise and sunset the sun itself as well as the surrounding sky appears red.
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