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Why is February 28th celebrated as NATIONAL SCIENCE DAY

“In the month of April 1923, Professor Raman’s distinguished student, K.R.Ramanathan, initiated some experiments on the scattering of light by water. The experiment was done using sunlight, and the scattered light was seen as a track in the transverse direction, and using a system of filters, the scattered light was examined. The filters were arranged in such a way that when the incident light was passed through one of the two complementary filters and the scattered light was viewed through the other filter, no track should have been visible at all. Some track however could be observed, and was attributed to a
weak fluorescence of the impurity molecules. Ramanathan himself wrote later that it was Professor Raman himself, and none other, who was not satisfied by the explanation based on the fluorescence model and that he (Raman) wondered if the track observed was due to some characteristic molecular scattering. The same effect was observed later in many organic liquids by K.S.Krishnan, another of Raman’s distinguished students.
Although I will not go into the details, there was a certain similarity in the explanation Raman had in mind with that of what is known as the Compton Effect. In the winter of 1927, Professor Raman went to Waltair for a short visit; he derived a formula for molecular scattering now known as the Compton-Raman formula.

In January 1928, another associate of Professor Raman, Venkateswaran, observed that in pure glycerin,the scattered light was greenish in color, instead of the usual blue. Moreover, the radiation was strongly polarized. In the last week of January, Professor Raman asked K.S.Krishnan to repeat these experiments under more carefully controlled conditions. K.S.Krishnan was at that time doing completely theoretical work and Professor Raman advised him that it was not healthy for a man of science to stay out of touch with actual experiments for any significant length of time. Krishnan also reported the same type of findings as Ramanathan did, and Professor Raman personally verified all the observations.
Professor Raman was extremely excited about the findings, since he understood exactly what this just discovered phenomenon was. On 16th February, Raman sent a note to Nature, suggesting that the modified radiation observed in these scattering experiments could be due to certain molecular fluctuations. Yet, however, the phenomenon was not fully understood.
On the 27th February, Raman set up an experiment in which he decided to view the track earlier thought to be due to fluorescence using a direct vision spectroscope.
The experiment could not be completed that evening, as by the time~ the experiment was set up, the sun had set! Next morning, February 28th, 1928, when the experiment was done personally by Professor Raman, he found that the track contained not only the incident color but also another one separated by a dark region. This was the very first observation of what is known as the RAMAN EFFECT.
An announcement was made to the Associated Press on 29th February (in the leap year) and Professor Raman sent a note to Nature on March 8th announcing his discovery along with a complete explanation. Several laboratories in the world, on coming to know of this experiment, repeated such measurements and confirmed the findings. The recognition that followed in terms of the Nobel prize was almost inevitable, despite the fact that Raman was an Indian.
As you would know, the Nobel prize for Physics is given each year at Stockholm, Sweden, on the 10th of December, and the award is announced for that year about a month in advance.
The Raman effect involves an exchange of a quantum of energy between a molecule and the electromagnetic radiation. Molecular energy levels are quantized, and this means that a molecule cannot possess an arbitrary amount of energy. The energy may be due to various reasons, and one may thus speak of the electronic energy, rotational energy or the vibrational energy of the molecule. A molecule may undergo transition from one energy state to another only by absorbing or emitting a discrete amount of energy. Raman Spectroscopy involves the study of such transitions. This is now an extremely specialized branch of spectroscopy and has undergone enormous developments. Raman spectroscopy is rarely done using sunlight as a source. Now, LASER radiation is employed and it has very many fascinating applications, and the technique is known as the Laser-Raman Spectroscopy.