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Why is the sky blue?

Why is the sky blue? The sky is blue because molecules in the air scatter blue light from sun. The white light from the sun is mixture of all colors from the rainbow. Mr. Issac a Newton used a prism used a prism to separate the colors and to also form a spectrum. The colors of light are differentiated by their different wavelengths.

The visible part of the spectrum ranges from red light with a wavelength of about 720 nm, to violet with a wavelength of about 380 nm, with orange, yellow, green, blue and indigo between. The three different types of color receptors in the retina of the human eye respond most strongly to red, green and blue wavelengths, giving us our color vision. The first steps toward correctly explaining how the sky is actually blue were taken by John Tyndall in 1859. He was the first to discover that light passes through a clear fluid holding small particles in suspension. Tyndall’s discovery is correctly called the Tyndall effect but it ‘s more commonly known to physicists as Rayleigh scattering; after Lord Rayleigh, who studied it in more detail a few years later.

He showed that the amount of light scattered is inversely proportional to the fourth power of wavelength for sufficiently small particles. It follows that blue light is scattered more than red light by a factor of (700/400)4 = 10. Tyndall or Rayleigh thought that the blue color in the sky was small particles of dust and droplets of water vapor in the atmosphere. The case was finally settled by Einstein in 1911, who calculated the detailed formula for the scattering of light from molecules; and this was found to be in agreement with experiment. He was even able to use the calculation as a further verification of Avogadro’s number when compared with observation. The molecules are able to scatter light because the electromagnetic field of the light waves induces electric dipole moments in the molecules.

If shorter wavelengths are scattered most strongly, then there is difficult way as to why the sky does not appear violet, the color with the shortest visible wavelength. The spectrum of light emission from the sun is not constant at all wavelengths, and additionally is absorbed by the high atmosphere, so there is less violet in the light.

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