Cloud is a large collection of very small water droplets or ice crystals. The droplets are so small and light that they can float in the air. All air contains water, but near the Earth’s surface typically is in the form of invisible gas called water vapor. When the warm air rises, it expands and cools. Clouds reflect the light of the sun, which makes it white.
White Clouds: Since light is distributed in the form of different wavelengths, each color has its own unique wavelength. Clouds are white, because they are water droplets or ice crystals are large enough to scatter light in seven wavelengths (red, orange, yellow, green, blue, indigo and violet), which combine to produce white light.
Appearance of Clouds: Clouds are composed of tiny water droplets or ice crystals, typically a mixture of both. Water and ice scatter all the light that makes the clouds appear white. If the clouds get heavy enough or high enough to cover all do not make it to the end, hence the gray or dark appearance. Also, if there are other cloud around their shadows can be added to gray or gray appearance.
Cloud Speed: The clouds move with the wind. High cirrus clouds are pushed in the jet stream, sometimes travelling more than 100 miles per hour. When the clouds are part of the storm, they usually travel 30 to 40 miles/h.
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