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Author Topic: Why don't you see red clouds in the day?  (Read 1163 times)


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Why don't you see red clouds in the day?
« on: 26/03/2011 17:30:02 »
Gordon Kubank  asked the Naked Scientists:
In Australia we often see red sunrises & sunsets.

So why do the clouds reflect red light when the sun shines on the underside of the clouds, but the clouds look grey when the sun is above them?

You never see red clouds during the day.

Is it the water molecules that reflect the red rays whereas the same sunlight makes the air above the clouds look blue?
Gordon Kubank
Sunshine Coast, Qld

What do you think?
« Last Edit: 26/03/2011 17:30:02 by _system »


Offline yor_on

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Why don't you see red clouds in the day?
« Reply #1 on: 26/03/2011 19:54:58 »
The lower the sun stands at the horizon the longer the suns rays has to travel in the air before they will hit your eyes. At such times the air molecules filter/scatter away the shorter wavelengths, leaving only the longer predominantly red (yellow, orange) wavelengths to reach you. So it's a question about how long the 'light waves' travel inside the atmosphere. That's also why clouds looks predominantly 'white' when the sun stands right above you. It's the shortest pathway for those beams and so they can keep all their 'wavelengths' intact and the result becomes 'white' to us.

But, this plays a role too:

"The water droplets in clouds are usually the perfect size to reflect all the visible colors of light that hit them, creating the appearance of white.  The color white is really the presence of all colors.

In a similar fashion, the sky is blue because nitrogen, which makes up most of our atmosphere, has molecules which are much smaller than (cloud) water particles which reflect all visible colors of light, but exactly the right size to reflect light rays from the blue side of the spectrum.  The blue light bounces from molecule to molecule until the entire sky seems to be blue."

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Why don't you see red clouds in the day?
« Reply #1 on: 26/03/2011 19:54:58 »


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