The optical phenomenon responsible for the blue colour of sky is

The optical phenomenon responsible for the blue colour of sky is

dispersion
reflection
refraction
scattering
This question was previously asked in
UPSC CAPF – 2022
The correct answer is D, scattering.
The blue colour of the sky is primarily caused by the scattering of sunlight by molecules and tiny particles in the Earth’s atmosphere.
This phenomenon is explained by Rayleigh scattering, which states that the amount of scattering is inversely proportional to the fourth power of the wavelength. Shorter wavelengths (like blue and violet) are scattered much more effectively than longer wavelengths (like red and orange).
When sunlight enters the atmosphere, the blue light is scattered in all directions by the atmospheric particles, making the sky appear blue. Our eyes are more sensitive to blue light than violet, contributing to the perception of a blue sky.
Dispersion is the splitting of white light into its constituent colours due to different wavelengths having different refractive indices in a medium (like in a prism or rainbow). Reflection is the bouncing of light off a surface. Refraction is the bending of light as it passes from one medium to another. While refraction plays a role in atmospheric phenomena like mirages, it’s scattering that causes the blue sky.
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