Air Molecules, Dust and Haze

Air molecules are much smaller in size than dust and haze particles, and are known as "Rayleigh Scatterers". This means that air molecules are more efficient in scattering the shorter wavelengths of light. Rayleigh scattering is responsible for the blue appearance of a clear sky.

On the other hand, dust and haze particles are called "Mie Scatters", which means they scatter all wavelengths of visible light equally. A hazy white sky, for example, is a result of Mie scattering.