By Sunil Bhardwaj


When molecular sample is placed in an intense beam of monochromatic radiations, it transmit the entire incident light. In this case molecule gets excited and immediately returned to ground state. The returning molecule takes place with emission of light in all the directions. This type of scattering of light is known as Rayleigh scattering.

In 1923, smekel theoretically predicted that if the substance in solid liquid or gaseous state is irradiated with monochromatic light, the scattered light must contain radiations with the different frequencies than that of incident.

In 1928, Sir C.V.Raman found that the scattered light must contain some lines which have the frequency more than incident and some lines possess the frequency less than incident. The lines which have frequency less than incident are called Stokes Lines and those which have more than incident are called Antistoke Lines. These stoke and anti-stoke lines form Raman Spectrum.$$ \triangle \nu ={ \nu }_{ incident }-{ \nu }_{ scattered } $$

Polarisibility in a molecule

\(\triangle \nu\) is positive means \({ \nu }_{ incident }>{ \nu }_{ scattered }\) hence stoke lines.

\(\triangle \nu\) is negative means \({ \nu }_{ incident }<{ \nu }_{ scattered }\) hence Antistoke lines.

Polarisibility in a molecule

MCQ on Spectroscopy from Physical Chemistry
Prof. Gianfranco Coletti

Shared publicly - 2019-08-23 00:00:00

Don’t want your columns to simply stack in some grid tiers? Use a combination of different classes for each tier as needed. See the example below for a better idea of how it all works.

Prof. Maheshwar Sharon

Shared publicly - 2019-08-24 00:00:00

For grids that are the same from the smallest of devices to the largest, use the .col and .col-* classes. Specify a numbered class when you need a particularly sized column; otherwise, feel free to stick to


Shared publicly - 2023-02-28 11:09:52

this is


Shared publicly - 2023-02-28 10:48:10