Why the colour of sky is blue

The blue color of the sky is primarily due to a phenomenon called Rayleigh scattering. Here’s how it works:

Rayleigh Scattering: When sunlight enters the Earth’s atmosphere, it encounters gas molecules and other particles. These particles scatter sunlight in all directions, but the scattering is not uniform for all wavelengths of light. Instead, shorter wavelengths (blue and violet) of visible light are scattered more efficiently than longer wavelengths (red and orange).

Shorter Wavelengths Scattered More: The reason shorter wavelengths are scattered more efficiently is because their interaction with gas molecules and particles is more pronounced due to their smaller size. As sunlight passes through the atmosphere, the shorter blue and violet wavelengths are scattered in all directions by gas molecules and particles in the atmosphere.

Dominance of Blue Light: Since blue light is scattered more effectively, it tends to be scattered in all directions, including downward towards the Earth’s surface. This leads to a higher concentration of blue light reaching our eyes from all directions, giving the sky its characteristic blue appearance.

Angle Dependency: The intensity of Rayleigh scattering varies with the angle of the sunlight. When the sun is directly overhead (near zenith), the path through the atmosphere is shorter, and the blue light scattered from overhead reaches our eyes more directly, intensifying the blue color of the sky. At sunrise and sunset, when the sunlight has to pass through a thicker layer of atmosphere, more of the shorter blue wavelengths are scattered away, leading to the reddish hues observed during these times.