Thin clouds look white. A thick rain cloud looks grey, or even dark. Why the difference?
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
Thin clouds look white. A thick rain cloud looks grey, or even dark. Why the difference?
Need a reminder? The key ideaShow
Very small particles, such as air molecules, scatter light in proportion to : blue far more than red. Large particles, such as cloud drops, scatter all colours about equally, which looks white. The Tyndall effect is the path of a beam made visible by scattering.
The worked solution
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Step 1. Thin clouds. Their droplets are large, so they scatter all colours about equally. An even mix of all colours looks white.
Step 2. Thick clouds. They scatter the light the same way, but they are so deep that little light gets through to the bottom. From below, they look grey or dark.
Answer: both scatter all colours equally; a thick cloud lets little light through.
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