Why are Clouds White? Raman Effect & Rayleigh Scattering

  • Thread starter rishch
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In summary, there are two explanations for the color of clouds - one states that the particles in the cloud are big and reflect white light, while the other explains that the varying sizes of water droplets in the cloud create different colors - blue, green, and red - that combine to make white. The Raman effect also plays a role in the color of the sky, as the scattered light is the same as the incident light. The white light is scattered by the larger water droplets, which are bigger than the wavelengths of visible light. Additionally, clouds are held up in the air by buoyancy, as explained in the Scientific American article.
  • #1
rishch
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In one place I read that since the particles are big they reflect white light as is. But in another I read that they are made up of water droplets of varying sizes so,

small droplets: make blue
medium droplets: make green
larger droplets: make red

...and together they combine to make a white cloud. Which one is correct?

And also, under Raman effect it's given that in Rayleigh scattering the scattered light is the same as that of the incident light. But how. The sky is blue. This is because blue light is scattered. But the incident light is white? Or do they mean that the scattered light's wavelength does not change?
 
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  • #2
I've only read that water droplets are larger than the wavelengths of visible light and therefore reflect or scatter all of it equally.
 
  • #3
diffuse reflection off water droplets.
 
  • #4
May I join in along a sideline.

Clouds consist of water droplets. What holds the cloud up in the air?
 
  • #6
Thanks Charmar.
 

1. Why are clouds white?

Clouds appear white because they reflect and scatter sunlight in all directions. This scattering of sunlight is known as Rayleigh scattering, which is responsible for the blue color of the sky. However, because clouds are made up of tiny water droplets or ice crystals, the scattered light is reflected equally in all wavelengths, resulting in the appearance of white.

2. How does the Raman Effect contribute to the whiteness of clouds?

The Raman Effect is a phenomenon in which light is scattered by molecules in a medium, causing a shift in the wavelength of the scattered light. In the case of clouds, the water molecules in the clouds can cause this scattering of light, resulting in a small contribution to the whiteness of the clouds.

3. Can clouds be any other color besides white?

Yes, clouds can appear in various colors depending on the size and composition of the particles within them. For example, if the particles are larger, they can absorb more light and appear darker, giving the clouds a grey or even black appearance. Additionally, the presence of pollutants or dust in the air can also give clouds a different color.

4. Are all clouds white?

No, not all clouds are white. Some clouds, such as cumulonimbus clouds, can appear grey or even black due to their thickness and high concentration of water droplets or ice crystals. Additionally, high altitude clouds, such as cirrus clouds, can appear in shades of orange, pink, or red during sunrise or sunset due to the scattering of light by the Earth's atmosphere.

5. Is the whiteness of clouds influenced by the time of day?

Yes, the whiteness of clouds can be influenced by the time of day. During the day, sunlight is more intense and can lead to a brighter appearance of white clouds. However, during sunrise and sunset, the angle of the sunlight causes the light to pass through more of the Earth's atmosphere, resulting in a reddish or orange tint to the clouds.

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