Question: Why are clouds white?

Steven Gardner answered on 19 Jun 2013:

Clouds are white because the droplets in them scatter light according to a theory called Mie Scattering. Mie scattering is roughly the same for all colours so all colours are scattered equally, so they appear white.

This is almost the same as why the sky is blue, in that case it’s due to a different kind of scattering called Rayleigh scattering. In Rayleigh scatter blue is scattered more than the other colours, which is why the sky appears blue. The difference between the two type depends on the size of the thing the light is scattering from. Bigger things scatter according to Mie scattering and smaller things according to Rayleigh scattering. So since water droplets are much bigger than the atoms in the air clouds are white and the sky is blue.