What makes the clouds go black?
Why are some clouds black and others white? Some clouds are white and some are “black” due to two chief reasons: 1) optical thickness and 2) viewpoint and/or background (contrast). Concerning optical thickness: it is a technical term that just means that a thicker cloud has more droplets of water for the light to scatter off of. This can be due to either the physical thickness of the cloud or the density of the droplets, or both. For a sufficiently thick cloud (that has sufficient optical thickness) a bunch of the light is scattered back in the general direction from which it came as well as sideways and forwards, to there’s just not as much light getting “through” the cloud to the ground. Up in the sky, thin clouds (like cirrus clouds) usually look white, but not thick clouds. The thicker ones look dark, but they are really just darker than the sky. It is the contrast that makes them look “black”. This optical thickness is different than saying that an optical component like a lens is
