Why are Clouds white?


by cragar
Tags: clouds, white
DaveC426913
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#19
May27-11, 10:35 AM
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Zeal: clouds are formed of droplets in the microns size, very close to the wavelength of light where Mie scattering occurs. Rainbows are formed of droplets many times larger than the wavelength of light, where normal refraction occurs.

You see clouds all the time but you only tend to see rainbows when there's actual rain.

I learned about Mie scattering with a 30 second visit to Wiki.
DaleSpam
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#20
May27-11, 12:01 PM
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Quote Quote by ZealScience View Post
How can rainbow be created if droplet diffract different frequencies exactly the same?
Diffraction is not relevant AFAIK. The small water droplets scatter all frequencies approximately the same. The larger droplets refract different wavelengths differently. You are mixing up different phenomena. Refraction is different from scattering is different from diffraction.
ZealScience
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#21
May28-11, 07:02 AM
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Quote Quote by DaleSpam View Post
Diffraction is not relevant AFAIK. The small water droplets scatter all frequencies approximately the same. The larger droplets refract different wavelengths differently. You are mixing up different phenomena. Refraction is different from scattering is different from diffraction.
Sorry, I mean refract, misprinted. But why doesn't scattering like that won't cause polarization of light? Because light scattered by air molecules is polarized.
DaleSpam
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#22
May28-11, 07:11 AM
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I don't know anything about the polarization of scattered light. Sorry. Perhaps the link on Mie scattering has something.
ZealScience
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#23
May28-11, 07:14 AM
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Quote Quote by DaleSpam View Post
I don't know anything about the polarization of scattered light. Sorry. Perhaps the link on Mie scattering has something.
Sorry, I don't know either, I just can't quite understand it, so I'm asking it. Because air molecules polarizes light by reflection. But the reflection of light is similar pattern to the mie scattering that I looked at. Sorry for my deficiency of knowledge in this area. But I just don't quite get it. Probably I can start a thread about that.
Redbelly98
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#24
May30-11, 08:49 AM
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The number of scattering events is important too. For just one scattering event (rainbows, blue sky), polarization and color-separating effects are easily visible.

For many many scattering events (clouds, whitewater), the polarization gets randomized, and colors get mixed together.


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