The reason skies appear blue is primarily due to a phenomenon known as Rayleigh scattering. When sunlight passes through the Earth's atmosphere, it interacts with the gas molecules (mainly nitrogen and oxygen) present in the air.
Here’s a breakdown of the reasons you mentioned:
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Natural Color of Molecules: While oxygen and nitrogen themselves do not have an intrinsic blue color, they scatter light differently based on wavelength.
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Filtering Reds and Yellows: This statement is somewhat misleading. It's not that they filter out the reds and yellows per se, but rather that shorter wavelengths of light (like blue and violet) are scattered more effectively than longer wavelengths (like red and yellow).
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Scattering Mechanism: The correct explanation is that oxygen and nitrogen molecules scatter the shorter wavelengths of light (blue and violet) much more than the longer wavelengths (yellow and red). Due to this scattering, blue light is dispersed in all directions, making the sky appear predominantly blue to our eyes. Although violet light is scattered even more than blue light, human eyes are more sensitive to blue light and less sensitive to violet light, and some of the violet light is absorbed by the ozone layer. This results in the sky appearing blue.
In summary, the blue color of the sky is due to Rayleigh scattering, where shorter wavelengths of light are scattered more than longer wavelengths by the molecules in the Earth's atmosphere.
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