The optical phenomenon responsible for the blue color of sky is

The blue color of the sky is primarily due to the optical phenomenon known as scattering, specifically Rayleigh scattering [4]. Sunlight consists of various wavelengths; as it enters Earth's atmosphere, it interacts with air molecules and fine particles that are smaller than the wavelength of visible light [1]. These particles are more effective at scattering shorter wavelengths, such as blue and violet, in all directions compared to longer wavelengths like red [2]. Although violet light is scattered even more than blue, the human eye is more sensitive to blue light, and some violet is absorbed in the upper atmosphere [1]. Consequently, the scattered blue light dominates our vision when we look at the sky [1]. Without an atmosphere to facilitate this scattering, the sky would appear dark [1]. Other phenomena like dispersion involve splitting light into a spectrum, while scattering involves the redirection of light by particles [4].

Sources

1. [2] FUNDAMENTALS OF PHYSICAL GEOGRAPHY, Geography Class XI (NCERT 2025 ed.) > Chapter 8: Solar Radiation, Heat Balance and Temperature > The Passage of Solar Radiation through the Atmosphere > p. 68
2. [4] https://www.nesdis.noaa.gov/about/k-12-education/atmosphere/why-the-sky-blue
3. [1] Science , class X (NCERT 2025 ed.) > Chapter 10: The Human Eye and the Colourful World > 10.6.2 Why is the colour of the clear Sky Blue? > p. 169