Science Day and India's Nobel Prize-Winning Scientist
Kolkata, West Bengal
India's Science Day is celebrated on February 28th. Why was this date chosen?
A valuable discovery occurred on this day. The inventor was scientist Chandrasekhar Venkata Raman (C.V. Raman). First, we must mention that discovery. The discovery relates to optics. Nothing can be seen in the darkness of night. We can see when the sun rises. Everything is visible in sunlight. What kind of light is that? In that light, there are seven colors. That is, the sunlight is made up of seven visible colors. Those colors are very familiar: violet, indigo, blue, green, yellow, orange, and red. "Beni Ahsakola" is a mnemonic, and in English, the first letters of the colors can be expressed as "VIBGYOR." Each colored light has its own unique identity. They have specific frequencies (or wavelengths). The frequency of red light is different from that of violet light. The frequency of red light is the lowest, while its wavelength is the longest. When the frequency is higher, the wavelength decreases (frequency is inversely proportional to wavelength). The frequency of violet light is the highest. The "Beni Ahsakola" is made up of the seven colored lines. This pattern or design of colors is the "spectrum" of the sun's white light. With the help of a spectrometer, we can see such a spectrum with the naked eye. What is this instrument like? Its main part is made of a prism. The prism inside the instrument separates the incident light rays into different parts. Based on frequency or wavelength, the seven lights become distinct. The traces of the light rays appear in the spectrum. At that time, we can see many kinds of light lines in the spectrum.Now for another point. The white light of the sun is actually a combination of multi-colored light (chromatic light). It consists of seven different wavelengths (or frequencies) of light. Violet color (or red color) has a specific frequency (or wavelength), meaning it is monochromatic light (monochromatic light).The phenomenon of light scattering is associated with the creation of a glow when light passes through a medium. Conversely, it creates shadow. When light interacts with matter at a very small scale, a different kind of occurrence happens. When light waves scatter on extremely small particles, light is diverted from its original path. After scattering, the light spreads in different directions. This scattering phenomenon is known as ‘scattering of light’ (scattering). How scattering occurs was explained by the British scientist Lord Rayleigh (Lord Raleigh), who also received the Nobel Prize for this work (1902).According to Rayleigh's scattering theorem, when particles (like liquid droplets, aerosols, or gases) scatter light, the frequency of scattered light remains unchanged. In other words, scattering maintains the original light's frequency. However, this general principle was challenged by an Indian scientist. The nature of light scattering was fundamentally changed when Sir C. V. Raman, on February 28, 1928, discovered that when monochromatic light passes through a transparent medium such as water, kerosene, benzene, glycerin, or even natural gases, it scatters, resulting in light of a different frequency.What is the result? The original light frequency changes. That is, the scattered light transforms into three different colors. This kind of scattering, where there is a change in the frequency of light, is termed the ‘Raman Effect.’ The three-color spectrum resulting from light scattering is known as the Raman spectrum. This phenomenon has profound implications in many fields of daily life.Scientist C. V. Raman published his findings in the scientific journal "Proceedings of the Indian Academy of Sciences." He observed that the three lines in the scattered light spectrum significantly differ from the original light spectrum. This finding was entirely novel and astonishing. Raman named the two shifted lines in the spectrum the Stokes line (Stokes line, lower frequency) and the Anti-Stokes line (Anti-Stokes line, higher frequency). He revealed a crucial fact that the position of these two lines depends on the chemical properties of the scattering medium.What kind of chemical properties influence this? It depends on the atomic properties, molecular composition, configuration, electrical, and magnetic properties. Additionally, the intensity and brightness of these lines depend on the physical properties of the scattering medium, such as density, pressure, viscosity, and elasticity.Raman conducted numerous experiments on various substances, establishing the significance of the Raman Effect. Experiments have been conducted in many laboratories across India and abroad. Over the past fifty years, there have been remarkable advancements related to the ‘Raman spectrum.’ Its applications can be seen in all scientific fields today. The Raman spectrum can analyze the chemical properties of liquids, gases, and solids. This helps us gather a lot of information about the substances. It helps determine the quality of food substances, flavors, and properties of valuable materials (such as gold, silver, diamond, etc.) as well as their pricing. Many applications exist in biochemistry, pharmacology, and in various fields of medicine. It can help analyze the structure and properties of biological cells. It can help determine the composition of various biological materials and substances in the human body.Today, in almost every country, government agencies for drug and food control rely on Raman spectroscopy to determine the quality of food products and pharmaceuticals. This ensures that only pure products are sold in the market.Why is the ‘Raman Effect,’ which refers to this special type of light scattering, significant?Sir Raman provided a written response. At that time, there were many debates regarding the nature of light, its behavior, and various related phenomena. The culmination of these debates led to the discovery of quantum theory. The German scientist Max Planck (Karl Ernst Ludwig Marx Planck, 1858 - 1947) was the proponent of this theory (Nobel Prize winner, 1918). According to this theory, light consists of a certain kind of energy. Photons make up this energy. Light does not emerge from any substance in a continuous manner. Instead, energy is emitted in packets or quanta. The name of this energy packet is ‘quanta.’ The phenomenon of light emission in packets is called ‘the quantum theory of light.’ Various experiments have consistently supported this principle.The scientist Einstein also contributed to this theory's development. According to quantum theory, the frequency of scattered light is associated with the energy of photons in a specified manner. This relationship can be expressed mathematically as E = hv, where v is the frequency, and h is a constant known as Planck's constant.Through quantum theory, Sir C. V. Raman explained the phenomenon of his discovery, the ‘Raman Effect,’ and articulated its various implications. Raman's discovery significantly impacted the global scientific community. For his discovery, he was honored with the Nobel Prize in Physics (1930). Many advanced instruments have since been developed based on his discovery. For instance, resonance Raman spectroscopy, stimulated Raman spectroscopy, and surface Raman spectroscopy. Various applications exist in chemistry, biochemistry, and pharmacology. Raman spectroscopy is used widely for analyzing substances.The contributions of Sir C. V. Raman to the scientific world are highly valuable. In memory of his discovery, February 28 is celebrated as National Science Day in India.Sir C. V. Raman led an exceptionally productive life. He was a brilliant student. He was born in Madras (November 7, 1888). His father was a teacher, Chandra Shekhar Ayer, and his mother was Parbati Devi. At the age of 18, he graduated with a B.A. from Presidency College, Madras, with honors (1904). Afterward, he completed his M.A. in physics with first-class honors. Following this, he moved to Kolkata for work rather than pursuing academia or research. He took a government job in the Accountant General's office. Even at a young age, Raman showed great interest in many scientific subjects. When he was just 18, his first research paper was published in a London journal. Because of this research, he gained recognition in the global scientific community at a young age. Alongside his job, he studied science. He tried to conduct research as well. The then vice-chancellor of Calcutta University, Chandra Ashutosh Mukhopadhyay, provided him with the opportunity to teach at the university. Later, in 1914, he founded the University Science College in Kolkata. He served as the head of the department. Calcutta University conferred upon him the Doctor of Science degree (1921). Subsequently, he was elected a fellow of the Royal Society in London (1924).The then British government of India honored him with the title ‘Sir’ (1929). He served as the director of the Indian Institute of Science in Bangalore for a long time (from 1933 to 1948). Besides his work in optics, he made significant discoveries in acoustics and magnetism. He conducted many experiments on the behavior of light in various chemical substances. One noteworthy research paper deserves mention: “On the Molecular Scattering and Extinction of Light in Liquids and the Determination of Avogadro Constant, Philosophical Magazine, 213-224, 1923.”Many of his research papers were published in the internationally renowned journal "Nature." On November 21, 1970, the celebrated scientist Sir C. V. Raman passed away.In memory of the day of the discovery of the Raman Effect, February 28 has been declared National Science Day in India. Since 1988, this day has been opened to all scientists across India. It serves as a special occasion to promote and disseminate science in the country.
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