Saquib Salim

National Science Day is celebrated every year on 28 February. On this day in 1928, Sir C. V. Raman discovered the Raman Effect, or Raman Scattering of Light, a phenomenon that changed man's understanding of physics. Ramans was conferred a Nobel Prize for Physics in 1930, the first to an Asian. Raman had placed India on the map of global science.

National Science Day

C. V. Raman’s student and associate Prof. K. S. Krishna recalls the great day: “Next afternoon on the 28th, I (K. S. Krishnan) went to the Association. Professor (C. V. Raman) was already there and we proceeded to examine the influence of wavelength of the incident light on the phenomenon. It was then that the Professor thought of examining the track of the modified scattering with a direct vision spectroscope. I was very skeptical as to whether one would be able to observe anything at all because I remember that 3 or 4 years previously (1924 оr 1925) Prof. Raman wanted to record the spectrum of the "weak fluore-scence" and asked Venkateswaran to do it using a constant deviation spectrograph. Even after prolonged exposure, Venkateswaran failed to record any spectrum.

“The great shout or really squeal that Professor gave when he made the observation is unforgettable. He said that there was a new patch of colour in the spectro-scope and that there was a definite gap between the spectrum due to the incident light and the new one which he interpreted as that due to the modified scattering. I too saw it with great happiness and satisfaction. Professor immediately asked me to photograph the modified spectrum using the baby quartz (Hilger) spectro-graph which I proceeded to do. The experiment was quite successful. We then repeated the experiment using monochromatic light from a quartz mercury vapour lamp with all the radiation excepting the blue cut off with filters. After a long exposure, the spectrum of the modified scattering exhibited itself in all its glory in the form of a series of beautiful discrete lines.

The Nobel award ceremony at Stockholm in 1930

“I can say that the Professor saw the effect visually in a spectroscope for the first time while I had the privilege of recording it for the first time on a photographic plate so that the world of science could believe that this effect did exist. I must confess that I had carried out dutifully all the experiments that the Professor asked me to do. If I were immodest I can say I executed them rather well. As I said before, those were wonderful days and all that we did remained permanently engraved in my mind and I recorded them carefully in my diary.”

Raman’s discovery is one of the foundational blocks of Quantum Physics and explains the behaviour of photons. Raman's discovery was remarkable as he carried out the research in India, a British Colony, by the Indians and with scanty resources. Raman later recalled, “The essence of science is the study of some natural phenomenon, independent thinking, hard work and not (necessarily) equipment. When I got my Nobel Prize, I had spent hardly Rs. 200/- on my equipment, three items: a mercury lamp, a flask of benzene, and a direct vision pocket spectroscope.”

Indian Scientist, S. Ramaseshan, wrote, “On his first voyage to Europe in 1921, the visual beauty of the Mediterranean bewitched him. Lord Rayleigh was of the view that this blue was due to the reflection of the sky in the water. Raman disproved it by a simple experiment he did on board the ship. He quenched the sky’s reflection with a Nicol prism at the Brewster angle and found that the blue colour “far from being impoverished by suppression of the sky reflection was wonderfully improved thereby”. He showed thus, that the blue is due to molecular scattering and established quantitatively that the Smoluchowski - Einstein fluctuations were its basic cause. He then wrote the celebrated monograph The Molecular Diffraction of Light in 1922.”

Max Born, another Nobel Laureate, later said, “It was astounding to know that Raman realised as early as 1922 that the field equations themselves have to be quantized…. Raman’s mind leaps over mathematics.”

Raman started his research to understand the scattering of light in 1921 which ended on 28 February 1928. He was sure of his success and used to tell people that it would bring him a Nobel Prize.

In 1924, when Raman was elected a Fellow of the Royal Society someone remarked, “What next?”, he replied, “Of course a Nobel.” In 1925 Raman wrote to GD Birla to help him buy a spectrograph because, “If I have it, I think I can get the Nobel Prize for India.”

K S Krishna's Diary entry 

After his discovery, Raman was so sure of a Nobel that he booked two tickets, for him and his wife, to Stockholm in July. It must be noted that the Nobel Prize Committee meets in secrecy in early November and declares the prizes in late November. The ceremony is held in December. But, Raman booked his tickets even before the meeting for the prize.

Why was he so sure? She knew his discovery was revolutionary.

Raman’s discovery was reported to Nature, one of the most respected science journals, in the form of a letter on 8 March 1928. Prof R. W. Wood, the distinguished optical physicist of Johns Hopkins University, wrote in response to the letter in the jounal, “Prof Raman’s brilliant and surprising discovery; I have verified his discovery in every particular. Raman’s discovery thus makes it possible to investigate remote infra-red regions hitherto unexplored. It appears to me that this very beautiful discovery which resulted from Raman’s long and patient study of the phenomenon of light scattering is one of the most convincing proofs of the quantum theory.’’ 

Lord Rutherford in his presidential address to the Royal Society in November 1929 said, “It is clear that this new effect may be of great importance in determining the slow characteristic frequencies of molecules in the infra-red, which may be difficult to measure by other methods. This discovery, of great interest in itself, thus promises to open up a new field of experimental inquiry and throw valuable light on the modes of vibration and constitution of the chemical molecule. This discovery has attracted much attention, and a number of papers dealing with it have been published in all parts of the scientific world.”

The assessment was not wrong. Within a year, at least 150 academic papers discussing Raman Effect were published. By July 1930, the papers had gone up to 350!

The Italian Society of Sciences, Rome, awarded him the Matteucci Gold Medal for “the most important physical discovery of the year”. The British Government conferred a knighthood. The Faraday Society of London invited Raman to deliver the opening address at a meeting on “Molecular spectra and molecular structure”, and to lead the discussion. The University of Freiburg awarded a doctoral degree honoris causa, while the Physical Society of Switzerland elected him an Honorary Member.

India was a colony, the independence was still almost two decades away but Raman brought India to the notice of the world. Raman’s wife, Lokasundari Ammal, who accompanied him to Stockholm notes that on 10 December 1930 at the Nobel Banquet, “In replying to the toast. Sir Raman spoke of the glories of ancient India. He spoke of the great renunciation of Buddha, the royal ascetic and world teacher, and of his message of non-violence and love which embraced all living creation.”

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A year before at the University of Mysore, Raman told the students, “Self-determination will come, but we must prepare ourselves for it. It is no use asking for freedom if we are not prepared to pay the price for it.” Raman led by example.