Raman Effect


Raman effect
A new type of molecular scattering entirely
different from Rayleigh’s scattering was
discovered by Sir C.V. Raman in 1928. When
an intense beam of monochromatic light is
passed through a substance, the light is
scattered and the scattered light contains other
frequencies in addition to that of the incident
light. This is known as Raman effect. For the
above discovery Sir C.V. Raman was awarded
Nobel Prize on 10th December 1930.
When the scattered radiation is examined by a spectroscope, a number of new
lines are observed on both sides of the parent line corresponding to incident
frequency. The new lines are called Raman lines. The lines having lesser
frequencies than that of incident light are called Stokes lines.The lines having higher
frequencies than that of incident light are called Antistokes lines.
The difference between the frequency of any Raman line and the frequency of
the parent line is known as Raman shift. For a given scattering material, the Raman
shifts are the same, whatever be the frequency of the incident light.
Raman shift is used to analyse the chemical composition of different substances
and also to classify them according to their molecular structure.

The colour of the sea The blue colour of the sea is partly due to
reflection from the blue sky and partly by scattering of light by the
water molecules. Near the shore the sea is green because of the
sand in suspension which scatters blue and green light and also due
to the reflection of yellow light from the sand.

REF:Textbook of  Tamilnadu