Why is the sky Blue?

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[Physics FAQ] - [Copyright]

Original by Philip Gibbs May 1997.




** Why is the sky blue? **

A clear cloudless day-time sky is blue because molecules in the air scatter
blue light from the sun more than they scatter red light.  When we look
towards the sun at sunset, we see red and orange colours because the blue
light has been scattered out and away from the line of sight.

The white light from the sun is a mixture of all colours of the rainbow. 
This was demonstrated by Isaac Newton, who used a prism to separate the
different colours and so form a spectrum.  The colours of light are
distinguished 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 colour receptors in the
retina of the human eye respond most strongly to red, green and blue
wavelengths, giving us our colour vision.

-Tyndall Effect-

The first steps towards correctly explaining the colour of the sky were
taken by John Tyndall in 1859.  He discovered that when light passes
through a clear fluid holding small particles in suspension, the shorter
blue wavelengths are scattered more strongly than the red.  This can be
demonstrated by shining a beam of white light through a tank of water with
a little milk or soap mixed in.  From the side, the beam can be seen by
the blue light it scatters; but the light seen directly from the end is
reddened after it has passed through the tank.  The scattered light can
also be shown


Source: math.ucr.edu/home/baez/physics/General/BlueSky/blue_sky.html


why is the sky blue


Why is the sky blue? - Wikipedia, the free encyclopedia

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** Why is the sky blue? **

From Wikipedia, the free encyclopedia
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*Why is the sky blue?* may refer to:

· Rayleigh scattering, scattering of sunlight in the atmosphere
· Diffuse sky radiation solar radiation reaching the Earth's surface after
Rayleigh scattering
· /Why Is the Sky Blue?/, 1992 book by David West
· /Why Is the Sky Blue?/, 2007 book by Sally Grindley and Susan Varley

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