National Science Day: What is the ‘Raman effect’?

In 1986, the Government of India designated February 28 as National Science Day, to commemorate the announcement of the discovery of the “Raman effect”.

• National Science Day is an occasion to salute the talent and tenacity of our scientists. Their innovative zeal and pioneering research have helped India and the world.
• The theme of this year’s science day is “Women in Science”.
• Born on November 7, 1888, CV Raman was a physicist of Tamil origin who made a ground-breaking discovery in the spectrum of light scattering.
• The Raman Effect won scientist, Sir CV Raman, the Nobel Prize for physics in 1930.
• The nation honoured him with the Bharat Ratna, its highest civilian award, in 1954.
• CV Raman was appointed to be the first Indian director of Indian Institute of Science (IIS) in 1933.
• After India gained independence in 1947, Raman became the first National Professor of the country.

The Raman Effect

• The Raman effect is the inelastic scrambling of a photon by molecules which are energised to higher rotational energy or vibrational levels. This effect is also known as the Raman scattering.
• This phenomenon also forms the foundation of Raman spectroscopy which is utilised by physicists and chemists to know more information about materials.
• In 1928, Raman discovered that when a stream of light passes through a liquid, a fraction of the light scattered by the liquid is of a different colour.
• Raman conducted his Nobel-prize winning research at IACS, Calcutta.
• While he was educated entirely in India, Raman travelled to London for the first time in 1921, where his reputation in the study of optics and acoustics was known to physicists such as JJ Thomson and Lord Rutherford.
• A commemorative booklet prepared jointly by IACS and ACS on Raman mentions that his speciality was the study of vibrations and sounds of stringed instruments such as the Indian veena and tambura, and Indian percussion instruments such as the tabla and mridangam.
• Significantly, it notes that the Raman Effect is “very weak” — this is because when the object in question is small (smaller than a few nanometres), the light will pass through it undisturbed.
• But a few times in a billion, light waves may interact with the particle. This could also explain why it was not discovered before.
• In general, when light interacts with an object, it can be reflected, refracted or transmitted.
• One of the things that scientists look at when light is scattered is if the particle it interacts with can change its energy.
• The Raman Effect is when the change in the energy of the light is affected by the vibrations of the molecule or material under observation, leading to a change in its wavelength.

Significance of National Science Day:

• The sole message of National Science Day is to spread the message that Science and Technology should be applied in everyday life.
• On this day, scientists and science enthusiasts come together as programmes are held to bring the scientific community closer.
• Educational institutes also hold science fairs and science researchers get a chance to share their latest work.