What is the Rayleigh scattering?
Rayleigh scattering is the scattering of light by the particles present in the atmosphere. According to Rayleigh's scattering law, the amount of scattering of the light is inversely proportional to the fourth power of the wavelength. From the relation between scattering and wavelength, we understand that shorter wavelengths scatter more. Since blue light has a lesser wavelength than red light it scatters more.