What process is mostly responsible for the blue appearance of the sky?

a) refraction of light by clouds
b) scattering of light by air molecules
c) refraction of light by water molecules
d) obstruction of yellow light by pollutants

The scattering of light by air molecules is mostly responsible for the blue appearance of the sky. When light rays from the sun enter our atmosphere, it becomes significantly scattered to a different band of colors by the air particles. The most scattered color tends to be violet, however, our eyes are not sensitive to that color, therefore, it appears to be seen as blue.

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