National Science Day

Discovery of Raman Effect

National Science Day is observed annually on 28th February, the day Dr. C.V. Raman discovered the ‘Phenomenon of the Scattering of Light’ which has now come to be called, ‘The Raman Effect’. This day was constituted by the Government of India in 1986, on the recommendation of National Council of Science and Technology.

Definition

The Raman Effect is defined as the change of wavelength exhibited by some of the radiation scattered in a medium.

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Raman Effect Illustration

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Dr. C V Raman

Dr. C. V Raman wins Nobel Prize

Dr. C.V. Raman performed his experiment on scattering of lights while working at the Indian Association for the Cultivation of Science in Kolkata (IACS). For this discovery of his, he became the first Asian to get a Nobel Prize in the field of science in 1930.

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Indian Association for the Cultivation of Science in Kolkata (IACS)

Dr. K.S. Krishnan

Dr. Raman’s colleague, Dr. K. S Krishnan worked along with him. On February 28th  1928 evening, Raman had to go out of the laboratory on some pressing work. Dr. Krishnan who was researching in the laboratory, fortuitously observed for the first time the ‘Phenomenon of Scattering of Light’. An elated Dr. Krishnan recorded it in his worksheet. Dr. K.S. Krishnan thus became the first person to observe the ‘Raman Effect’.

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Dr. K. S. Krishnan

Rayleig

Before the discovery of Raman Effect, the prevalent concept was that of the English physicist Rayleig who in the 1870s tried to explain the blue colour of the sea and the sky.

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English Physicist Rayleig

Rayleig had expressed that the blue sky was the reflection of blue sea.

Dr. C.V Raman’s Research

Dr. C.V. Raman was not satisfied with this explanation. His fascination for the colours and their reasoning was further accentuated during sea voyage in 1921. He studied the scattering of the sun light by the air molecules to explain the blur colour of the sky. He also studied the scattering of light by the water molecules. This study led to his findings being termed the Raman Effect.

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Dr. C.V. Raman in his laboratory

Why the Sky and Sea appear blue?

When the sunlight hits the particles, the blue light is scattered the most and the red light the least. Due to this, both the sea and the sky appear blue.

He expressed how the water particles selectively absorb the red light and reflect the blue because of which we see water as blue.

Further Research

Dr. C.V. Raman continued his research in the phenomenon of light scattering, in other liquids and solids as well. This persistent research revealed the newer aspects of the behaviour of light.

Rigour and Diligence, not costly equipment

The apparatus with which Raman Effect was discovered cost less than Rs. 200 then. It consisted of a pocket spectroscope, a pair of complementary glass filters, a mirror, a condensing lens, and some liquid samples. It shows that even with simple instruments, it is possible to do path breaking research in pure sciences. What is needed is rigour and diligence and not just costly equipment.

National Science Day

This discovery of the ‘phenomenon of scattering of lights’, is regarded as one of the great achievements of modern science in India and is commemorated every year as National Science Day.

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