Why Do Some Clouds Have a Rainbow Hue?

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In summary, clouds form when moist air cools and water vapor condenses into liquid droplets. These droplets scatter and refract light, giving the cloud its opaque appearance. Rain clouds are darker because they are thicker and denser, while "rainbow" clouds can also form due to iridescence.
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rootone
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Clouds form in the atmosphere when moist air cools.
This is due to some of the water vapour as a gas condensing and instead forming into minute droplets of liquid water.
Why does this make the cloud opaque though? - both pure water vapour and pure liquid water are transparent.
 
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Unlike the water in a glass or swimming pool, clouds are not contiguous bodies of water. Rather, they are more like millions a water droplets scattered throughout with air in between. Whenever light passes through each of the individual droplets (which, of course, it does), the light is scattered and refracted--but only for a short distance because the refracted light will eventually hit another droplet.

So I guess what I'm trying to say is that photons that find themselves in clouds are constantly changing directions and the wavelengths of the light waves become so scattered that a cloud is seen, rather than just being a clear mass.
 
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I should add that one of the reasons why rain clouds are dark (not white) because they are thicker and denser. If you fly in a plane above a rain cloud, it will be white like any cloud on a sunny day because the sun is still beating down on it, giving the top of the cloud light to scatter. The droplets in the bottom of cloud (the part we see from the ground), however, don't receive enough light to scatter, thus, it appears grey and dark.
 
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1. Why do clouds appear white?

Clouds appear white because they are made up of tiny water droplets or ice crystals that reflect and scatter sunlight. This scattering of light creates the appearance of a white cloud in the sky.

2. Why do some clouds appear dark or grey?

Some clouds appear dark or grey when they are thicker and denser, causing them to absorb more light instead of reflecting it. This absorption of light makes the cloud appear darker in color.

3. Why do clouds sometimes have different shapes and sizes?

Clouds can have different shapes and sizes due to variations in temperature, moisture, and air pressure in different parts of the atmosphere. These factors affect how the water droplets or ice crystals form and arrange themselves to create different cloud formations.

4. Why do clouds appear to move in the sky?

Clouds appear to move in the sky because they are constantly being pushed and pulled by winds in the atmosphere. These winds are caused by differences in air pressure and temperature, which can also affect the shape and size of clouds.

5. Why do clouds appear opaque?

Clouds appear opaque because they are thick enough to block or scatter most of the sunlight passing through them. This is why they can also provide shade on a sunny day. The denser and more condensed the cloud, the more opaque it will appear.

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