National Science Day 2023: What Is Raman Effect? The Discovery Which Won CV Raman Physics Nobel

National Science Day 2023: CV Raman discovered the Raman Effect in 1928, and announced its discovery on February 28, 1928. To commemorate this, National Science Day is observed in India.

Indian physicist Chandrasekhara Venkata Raman (left) was awarded the 1930 Nobel Prize in Physics for his work on the scattering of light and for the discovery of the Raman Effect (right).

Source : Getty

National Science Day is celebrated annually on February 28 to commemorate the discovery of the Raman Effect. Indian physicist Chandrasekhara Venkata Raman was awarded the 1930 Nobel Prize in Physics for his work on the scattering of light and for the discovery of the Raman Effect.

Sir CV Raman announced the discovery of the Raman Effect on February 28, 1928. 

In 1986, the National Council for Science and Technology Communication (NCSTC) asked the then Government of India to designate February 28 as National Science Day. 

Interesting facts about CV Raman

Raman was born at Tiruchirapalli in Southern India on November 7, 1888. His father was a lecturer in mathematics and physics, as a result of which Raman was immersed in an academic atmosphere from the start.

In 1902, Raman entered Presidency College, Madras, and in 1904, passed his BA examination, winning first place and a gold medal in physics, according to the Nobel Prize organisation.

He obtained his MA degree in 1907, with the highest distinctions.

The two fields of investigation to which Raman dedicated his entire career were optics and acoustics. He carried out his earliest research in optics and acoustics while he was a student.

In 1922, Raman published his work on the "Molecular Diffraction of Light". This was the first of a series of investigations with his collaborators which ultimately led to discovery of the radiation effect which bears his name, the Raman Effect. 

In 1926, Raman founded the Indian Journal of Physics.  The physicist trained hundreds of students who found important posts in universities and government in India and Myanmar (Burma).

His work on Raman Effect was published in the Indian Journal of Physics in 1928. Raman was awarded the 1930 Nobel Prize in Physics for the discovery of the Raman Effect.

In 1924, Raman was elected a Fellow of the Royal Society of London. He has also been honoured with a large number of honorary doctorates.

In 1929, Raman was knighted. He became a member of the Pontifical Academy of Sciences, Vatican City, in 1961. 

In 1948, Raman founded the Raman Research Institute in Bangalore. It began as an institute privately owned by Raman, and is now funded by the government of India.

Other investigations conducted by Raman included experimental and theoretical studies on the diffraction of light by acoustic waves of ultrasonic and hypersonic frequencies, and those on the effects produced by X-rays on infrared vibrations in crystals exposed to ordinary light.

Raman had studied the spectroscopic behaviour of crystals. In 1948, he approached the fundamental problems of crystal dynamics in a new manner.

Raman was the uncle of Subrahmanyan Chandrashekhar, who was awarded the 1983 Nobel Prize in Physics, with William Fowler.

What is the Raman Effect?

When a light beam is deflected by molecules, its wavelength changes. This phenomenon is known as the Raman Effect. When a beam of light passes through a dust-free, transparent sample of a chemical compound, a small fraction of the light emerges in directions different from that of the incident beam. The wavelength of most of the scattered light remains unchanged. However, a small part of the light has wavelengths different from that of the incident light. This occurs as a result of the Tanan Effect. 

The effect was theoretically described for the first time in 1923, by Austrian physicist Adolf Smekal. 

Russian physicists Leonid Mandelstam and Grigory Landsberg had observed the phenomenon for the first time just one week before Raman. However, the Russian physicists did not publish their results until months after Raman, according to Britannica. 

One can think of incident light as consisting of particles, or photons, the energies of which are proportional to frequencies. In order to understand Raman scattering, one must consider the photons as striking the molecules of the sample.

Most of the encounters between the photons and molecules are elastic. In other words, the photons are scattered with unchanged energy and frequency.  

However, on some occasions, a molecule takes up energy from or gives up energy to the photons, as a result of which the photons are scattered with diminished or increased energy, respectively. Hence, they are scattered with lower or higher frequency. 

Therefore, the frequency shifts are measures of the amounts of energy involved in the transition between initial and final states of the scattering molecule. 

However, the Raman Effect is feeble. For instance, when an incident light traverses a liquid compound, the intensity of the affected light may be only 1/100,000 of the incident beam. This means that the wavelength of an extremely small portion of the incident light is changed. 

The pattern of the Raman lines depends on the type of molecular species. Also, the intensity of the Raman lines is proportional to the number of scattering molecules in the path of the light. 

Therefore, Raman spectra are used in qualitative and quantitative analysis.