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Scattering of Light in Atmosphere |
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When a beam of light falls in an atom, it causes the electrons
in the atom to vibrate. The vibrating electrons, in turn, re-emit
light in all direction. |
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As shown in fig (a). This process is called Scattering. Earth’s
atmosphere contains air molecules and other tiny particles.
When light from the sun passes through the atmosphere, it gets
scattered by the large number of particles in the intensity
of scatters light varies inversely as the fourth power of the
wavelength of light. |
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Fig (a) |
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(I) Blue color of
sky : Since the wavelength of *blue color is smaller
then the wavelength of red color (λv < λr ) ,
Scattering of blue light by particles in earth's atmosphere
is very large. For this reason we see a blue sky
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(II) Clouds are white:
A cloud is composed of large dust practices and water molecules
these large size d particles do not obey Raleigh law of Scattering.
Therefore, all colors or wavelength are scattered equally.
The overall result is a white cloud.
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Fig
(b) |
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(III) Sun looks reddish
at sunset or sunrise: At the time of sunset or sunrise
,the sun near horizon as shown in fig (b), the rays from the
sun must travel more blue is scattered from the sunlight.
The removal of blue leaves the transmitted light more reddish
in appearance. Therefore, sun looks reddish at the sunset
or sunrise.
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