This National Science Day, let the scattered light shine on C V Raman and his Raman effect
Great discoveries in science are often accompanied by stories that themselves become legends, whether they be true or false. The discovery of gravity is usually associated with the image of Newton sitting under an apple tree, and concepts of flotation and buoyancy conjure the image of a butt-naked Archimedes exclaiming “Eureka”.
National Science Day is celebrated in India on 28 February each year to mark the discovery of the Raman effect by Indian physicist Sir C V Raman on 28 February 1928.
For his discovery, Sir C.V. Raman was awarded the Nobel Prize in Physics in 1930.
History of National Science Day
In 1986, the NCSTC asked the Government of India to designate February 28 as National Science Day. The event is now celebrated all over the country in schools, colleges, universities and other academic, scientific, technical, medical and research institutions. On the occasion of the first NSD (National Science Day)(28 February 1987) NCSTC announced institution of the National Science Popularization awards for recognizing outstanding efforts in the area of science communication and popularization.
Celebration of National Science Day
National science day is celebrated on every year on 28 February.The celebration also includes public speeches, radio,TV , science movies, science exhibitions based on themes and concepts, watching the night sky, live projects, research demonstration, debates, quiz competitions, lectures, science model exhibitions and many more activities.
Themes of National Science Day
The theme of the year 1999 was “Our Changing Earth”.
The theme of the year 2000 was “Recreating Interest in Basic Science”.
The theme of the year 2001 was “Information Technology for Science Education”.
The theme of the year 2002 was “Wealth From Waste”.
The theme of the year 2003 was “50 years of DNA & 25 years of IVF – The Blue print of Life”.
The theme of the year 2004 was “Encouraging Scientific Awareness in Community”.
The theme of the year 2005 was “Celebrating Physics”.
The theme of the year 2006 was “Nurture Nature for our future”.
The theme of the year 2007 was “More Crop Per Drop”.
The theme of the year 2008 was “Understanding the Planet Earth”.
The theme of the year 2009 was “Expanding Horizons of Science”.
The theme of the year 2010 was “Gender Equity, Science & Technology for Sustainable Development”.
The theme of the year 2011 was “Chemistry in Daily Life”.
The theme of the year 2012 was “Clean Energy Options and Nuclear Safety”.
The theme of the year 2013 was “Genetically Modified Crops and Food Security”.
The theme of the year 2014 was “Fostering Scientific Temper”.
The theme of the year 2015 was “Science for Nation Building”.[1]
The theme of the year 2016 was on "Scientific Issues for Development of the Nation".
The theme of the year 2017 was "Science and Technology for Specially Abled Persons"[2]
The theme of the year 2018 was "Science and Technology for a sustainable future."
The theme of the year 2019 was on "Science for the People, and People for the Science"
The Raman effect
Bear in mind, this was mid-1920’s and India, firmly under British rule, was hardly a conducive place for research. Undeterred, Raman carried out simple but careful experiments, which were the first to show that light passing through liquids, solids even, can come out of them with a different wavelength. Only someone with hawk-like curiosity and observation could have made this discovery, because this anomalous scattering effect has existed in nature forever, but was so minimal that it escaped detection.
Most of the light that passes through a material emerges without any change in its wavelength. This scattered light, dubbed as ‘Rayleigh scattering’, is a common phenomena and is responsible for the blue colour of the sky among other things.
Let’s break down this effect to better understand it. Imagine light is made up of (and it is) particles called photon that carry energy. These photons when sent through a medium, collide with medium molecules, and emerge without any change in energy. These collisions are elastic in nature, and as such dont result in either the medium molecule or the hitting photon to gain or lose energy. But, some of these interactions exchange energy. And these rogue collisions result in the emerging photons of light with either reduced or gained energy — producing a scattered light profile which is now called the Raman effect.
Let’s break down this effect to better understand it. Imagine light is made up of (and it is) particles called photon that carry energy. These photons when sent through a medium, collide with medium molecules, and emerge without any change in energy. These collisions are elastic in nature, and as such dont result in either the medium molecule or the hitting photon to gain or lose energy. But, some of these interactions exchange energy. And these rogue collisions result in the emerging photons of light with either reduced or gained energy — producing a scattered light profile which is now called the Raman effect.
Since the number of such rogue collisions is low, the higher the concentration of molecules, the more enhanced the Raman effect, which explains why the effect is minimal in gases with low concentrations. Raman worked with liquids, which are denser than gases, and hence more prone to show these effects, and in 1928, submitted a report first to the Indian Journal of Physics and then to Nature — a journal synonymous with publishing many of the groundbreaking discoveries that have lead to Nobel Prizes.
Gathering scattered light to decipher material make-up
What Raman and his coworkers discovered is essentially a new kind of radiation — a signature that can be used for identifying materials, much like a fingerprint analysis. When a photon interacts with a molecule — a rogue collision, a molecule can use some of the energy of the photon, accessing a “mode” with higher energy. The loss of energy for the photon manifests as a change in wavelength, which is seen in the scattered light.
Sometimes, a photon may gain energy instead and this too manifests as a change in wavelength. Here’s the method in full glory: You shine a source of light that passes through a test material, and you collect the scattered light at the other end. Some of the scattered light would be of a different wavelength, and so a different colour. Depending on the specific material used — gas, liquid, solution or a mixture — the scattered light will show varying patterns, bands of different colour, and peaks at different wavelengths.
The Raman effect thus became a powerful tool for identifying material makeup and structure. It has been used for a variety of analyses — ranging from decoding what lunar soil is made up of, to analysing nuclear materials and industrial effluents. This practice of finding out what elements make up a certain material by using the principle of the Raman effect is dubbed Raman spectroscopy. What makes it such a powerful tool is that it’s not only easy to implement and understand, but also non-invasive.
Also, the tool has aged well. Lasers allows for a directed intense beam of light that leads to an enhanced spectra and clearer effects. Modern computers and data-handling tools have made Raman spectrography commonplace. From being a strong proof, yet again for the quantum nature of light to being a chemists standard tool, to becoming one of the first lines of attack for a materials scientist, the Raman effect was a momentous discovery then and is a bedrock of experimental physics now.
And it was first discovered, not by the guys in England who discovered the electron and nucleus, or the famed Copenhagen group — the fathers of quantum mechanics, but by a turbaned scientist in British-ruled India driven by curiosity.
And it was first discovered, not by the guys in England who discovered the electron and nucleus, or the famed Copenhagen group — the fathers of quantum mechanics, but by a turbaned scientist in British-ruled India driven by curiosity.