India celebrates National Science Day every year on 28 February to commemorate the discovery of the Raman effect by Sir Chandrasekhara Venkata Raman on this very day in 1928.
Raman was the first Indian Nobel prize winner (1930) in the field of science and what’s unique about him is that he got the prize for work done in India, at the Indian Association for the Cultivation of Science (IACS), Calcutta (Kolkata).
The theme for this year's National Science Day is “integrated approach in science and technology for a sustainable future". In this context, the Raman effect is a very good example as to how discoveries in the sciences (physics) can be used for a variety of technological applications, such as in the materials sciences, chemical and biochemical areas, pharmaceutical industry, and medicine.
Raman Effect
Raman’s interest in the scattering of light by molecules that ultimately led to the discovery of the Raman effect was triggered during his return journey to India by sea in 1921, after his first foreign trip to England as a Palit Professor at Calcutta University.
Prior to this, his major contributions had been in the field of acoustics and study of musical instruments.
While on board the ship, Raman noticed the dark blue colour of the sea, but was not satisfied by the explanation by Lord Rayleigh that it was due to the reflection of the blue colour of the sky.
Lord Rayleigh had explained the blue colour of the sky as due to scattering of light by molecules in air. These molecules, being much smaller in size compared to the wavelength of light, scatter light by different amounts depending on the wavelength.
The scattered intensity of light is directly proportional to the fourth power of the frequency. Consequently, blue light is scattered more than red. Hence the blue colour of the sky. This kind of scattering is called Rayleigh scattering and is an example of elastic scattering, where the frequency of the scattered light does not change.
Raman conducted many experiments to study the light scattered by sea water using instruments he had with him during his journey and published a couple of papers in the prestigious journal Nature by the time he reached India. He later published a book titled Molecular Diffraction of Light in 1922, reviewing the various aspects of scattering of light by gases, vapours, liquids, crystals, and amorphous solids, as was known until then.
Read More at https://swarajyamag.com/science/national-science-day-the-raman-effect-and-one-of-its-key-applications-explained
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