National Science Day (started in 1987) is being celebrated all over India on February 28. On this day in 1928, 80 years ago, C V Raman (1888-1970) made the remarkable discovery, now called the “Raman Effect”, a new phenomenon of scattering of light by molecules. In 1917, Raman gave up a lucrative career in the civil services to devote himself entirely to science. His discovery earned him the Nobel Prize in 1930 and India was on the map of the scientific world.

When Sir Ashutosh Mookherjee was appointed the vice-chancellor of Calcutta University, he invited Raman for the Palit Professorship in Physics. Raman accepted this offer in 1917 inspite of the fact that his monthly salary would be only Rs 600, which would be about half of what he was drawing in the civil services.

In 1921, Raman was invited to attend the University Congress at Oxford as a representative of Calcutta University. During the return journey, by ship, he was impressed by the blue colour of the Mediterranean Sea.

This captured his imagination. Lord Rayleigh had explained that the blue colour of the sky was due to scattering of light by air molecules; the sky would appear (dominantly) blue because the intensity of the scattered light is proportional to the fourth power of the frequency. The colour of the sea would then be due to the reflection of the sky! — this was the belief at that time.

Raman was convinced that the colour of the sea was due the scattering of light by water molecules. So, immediately after his return to India, he (and his students) started investigations on the molecular scattering of light. He set up his own apparatus. He collimated sunlight and used filters to get a monochromatic beam of blue light. This light would be incident on a liquid in a glass container and the scattered light would be observed in the perpendicular direction.

The colour of the scattered light was green — a reduction of frequency had occurred. A possible explanation was the idea of ‘fluorescence’, ie the incident light is absorbed by a molecule of the liquid and the molecule goes to a state of higher energy excited state. The excited molecule loses some energy by colliding with other molecules and goes to a lower level from which a transition to the ground state would emit light of a lower frequency.

Raman’s researches continued for many years. In February 1928, Raman and Krishnan were investigating more details of this ‘feeble fluorescence’ or later called ‘modified scattering’. They noticed that the scattered light was also strongly ‘polarised’. Such a possibility was permitted only  in quantum mechanics. Hence, this was a big discovery. On February 28, 1928, they observed that the scattered light (stokes lines) was actually separated from the incident light by a dark region in between.

Raman demonstrated his experiments in Calcutta and later in Bangalore. He immediately published the research paper in Nature on “A New Type of Secondary Radiation”. Two Russian physicists were also working on the same problem using quartz as scatterer; they had also discovered similar effect but were late in publishing their results. Raman was knighted in 1929 and was awarded the prestigious Nobel Prize for Physics in 1930, the first Asian to achieve this feat. After the discovery of lasers, Raman Scattering has been pursued vigorously. He was awarded Bharat Ratna in 1954.

The Indian Institute of Science (IISc) was established at Bangalore in 1911 by J N Tata.  The director of IISc was always an Englishman. When Martin Forster retired in 1933, Raman was appointed as the director and he was the first Indian to occupy that position. He established the physics department and started a vigorous research programme. Unfortunately, owing to several events, he could remain as director only for five years. He served from 1938 till his retirement in 1948 as a professor. During his tenure many brilliant physicists such as Homi Bhabha, Vikram Sarabhai, and G N Ramachandran worked under him.

Raman founded the Raman Research Institute in 1948. He did not want to accept government money for this purpose, so he collected money from philanthropists. Vikram Sarabhai helped him in contacting many industrialists to raise the money. Raman collected gems and minerals and set up a museum at RRI.

Sir C V Raman died on Nov 21, 1970 at the age of 82. His complete scientific papers have been brought out by the Indian Academy of Sciences in six volumes. Raman had a real passion for science. He knew exactly what problems to choose for his research and went into great depth to understand them. He was not satisfied by a mere superficial study. He was more like our classical musicians who spend days and nights learning the finer details of each raaga.

Sir Raman is one of the rare ‘gems’ of India. His legacy has provided the real inspiration for our younger generation. Raman said, “the quality of the Indian mind is equal to the quality of any other mind. What we lack is perhaps courage. We have developed an inferiority complex. We need the destruction of the defeatist spirit. We need a spirit of victory”.

(The writer is former chairman, department of physics, and dean, faculty of science, Bangalore University)