Raman effect

Raman effect is a change in the wavelength of light that occurs when a light beam is deflected by molecules.
When a beam of light traverses a dust-free, transparent sample of a chemical compound, a small fraction of the light emerges in directions other than that of the incident (incoming) beam.
Most of this scattered light is of unchanged wavelength.
A small part, however, has wavelengths different from that of the incident light; its presence is a result of the Raman effect.
The phenomenon is named after Indian physicist Sir C.V. Raman, who first published observations of the effect in 1928.
Austrian physicist Adolf Smekal theoretically described the effect in 1923.
It was first observed just one week before Raman by Russian physicists Leonid Mandelstam and Grigory Landsberg; however, they did not publish their results until months after Raman.

Light consists of particles called photons, whose energy is directly proportional to the frequency with which they travel.
When they strike molecules in a medium at high speeds, they bounce back and scatter in different directions depending on the angle with which they hit the molecules.
Most of these scatterings are elastic — the photons retain their energy and are deflected with the same speed as they were traveling with.
However, once in a while, the molecules of the medium light pass through, absorb or give energy to photons that strike them.
The light particles then bounce with decreased or increased energy, and thus, frequency.
When frequency shifts, so does wavelength.
This means that light refracted from a body, like the Mediterranean Sea or an iceberg, can appear to be of a different colour.

The effect is extremely negligible when measured and occurs in very low amounts.
But each medium contains a specific molecular scattering signature, related to the particular molecule and its numbers.
This gave birth to the field of Raman spectroscopy, which has extensive applications around the globe, and across fields.
It can help in determining chemical bonding structures, characterise materials, determine temperature, find out crystalline orientation, identify pharmaceutical chemicals, discover counterfeit drugs, identify pigments in old paintings and historical documents, and detect explosives using lasers from a distance.

C.V. Raman (or Sir Chandrasekhara Venkata Raman) was born on November 7, 1888, Trichinopoly, Tamilnadu.
His work was influential in the growth of science in India.
He received the Nobel Prize for Physics in 1930, for his discovery which was eventually named as the Raman effect or Raman scattering.
It was the first Nobel in Physics for a non-white person, and for an Indian scientist.
He died on November 21, 1970, Bangalore.

India celebrates National Science Day on 28 February every year since 1986 in honour of physicist C.V. Raman’s discovery of the Raman Effect, which gave Asia its first Nobel in the Sciences in 1930.
Every year, the day is celebrated with different themes to raise awareness about the importance of science in everyday life.
This year’s theme is ‘Women in Science’.

Scientists at the Mumbai-based Tata Memorial Centre have turned to Raman Spectroscopy to detect RNA viruses present in saliva samples.

The tool can only identify RNA viruses and not identify the specific one, it can be used only for screening.

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