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<title>Frequently Asked Questions</title>
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Click on a question to see its answer. Click on the question again to hide the answer.
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<h3><a href="javascript: toggleDiv('Q1');" style="text-decoration: none; ">Q1. Why is the sky blue?</a></h3>
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<p>Light is made up of electromagnetic waves.
The distance between 2 crests in this wave is called the wavelength.
White light contains all the colors of the rainbow.
The amount of light scattered for any given colour depends on the wavelength of that colour.
All the colors in white light have different wavelengths.
Red light has the longest wavelength.
The wavelength of blue light is about half that of red light.
This difference in wavelength causes blue light to be scattered nearly ten times more than red light. Lord Rayleigh studied this phenomena in detail. It is caused the Tyndall effect or Rayleigh scattering.
Lord Rayleigh also calculated that even without smoke and dust in the atmosphere, the oxygen and nitrogen molecules would still cause the sky to appear blue because of scattering.
When blue light waves try to go straight through an oxygen and nitrogen molecules, its light is scattered in all directions because of this collision.
This scattered blue light is what makes the sky blue.
All other colors (with longer wavelengths than blue light) are scattered too.
Blue light's short wavelength causes it to be scattered the most.
(The shorther the wavelength of the color, the more that color gets scattered by the atmosphere)
Actually, violet has the shortest wavelength of all colors. Violet is scattered even more than blue light. However, our eyes are much more sensitive to see blue than violet, therefore we see the sky as blue.
Very little visible light is absorbed by the atmosphere.
Blue sky: summary
Blue light's short wavelength causes it to get scattered around 10 times more by oxygen and nitrogen molecules than the longer wavelengths (like red) of the other colors visible to us.
The blue in the sky we see is scattered blue light
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<h3><a href="javascript: toggleDiv('Q2');" style="text-decoration: none; ">Q2. Why is the ocean blue?</a></h3>
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<p>Unfortunately, the simple explanation is made a bit more complex by whether you live in the United States or in the United Kingdom ;-)
If you live in the United States:
The ocean is blue because pure, clear water has a VERY light blue color.
If you live in the United Kingdom:
The ocean is blue because pure, clear water has a VERY light blue colour.
If you live anywhere else, you unfortunately have to decide for yourself which of these 2 explanations are correct ;-)
On a cloudy day when the sky appears grey, the ocean appears gray too (it reflects the sky).
High concentrations of plankton make the ocean appear blue-green.
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<h3><a href="javascript: toggleDiv('Q3');" style="text-decoration: none; ">Q3. Why are clouds white?</a></h3>
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Water and ice in clouds scatter all color wavelengths by the same amount. All colors are represented in this scattered light and clouds therefore appears white. (White light is made up of all colors, red, blue, violet, etc.)
(All wavelengths of light get scattered equally by drops of water and small clumps of ice.)
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