First let me explain briefly why we see blue sky
and then you will be able to answer your question
The sun produces white light, which
is made up of light of all colors: red, orange,
yellow, green, blue, indigo, violet. Light is a
wave, and each of these colors corresponds to a
different frequency, and therefore wavelength, of
When the white light from the sun
shines through the earth's atmosphere, it collides
with the gas molecules. These molecules scatter
The shorter the wavelength of
light, the more it is scattered by the atmosphere.
Blue light is scattered ten times more than red
light because it has a shorter wavelength.
you look up in the sky, the scattered blue light
is the light that you see.
Why does the
setting sun look reddish orange? When the sun is
on the horizon, its light takes a longer path
through the atmosphere to your eyes than when the
sun is directly overhead. By the time the light of
the setting sun reaches your eyes, most of the
blue light has been scattered out. The light you
finally see is reddish orange, the color of white
light minus blue.
So where does now the
blue sky end? Since our atmosphere is responsible
for the scattering of the light, the blue sky will
end where the atmosphere ends. Our atmosphere
reaches over 560 kilometers (348 miles) from the
surface of the Earth.
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