C. V. Raman

Lived 1888 – 1970.

It was discovered by C. V. Raman that light may give a small amount of energy to a molecule when it interacts with it. The molecule vibrates and the light changes colour as a result. The molecule may use the colour shift as a “fingerprint.”

Certain fingerprints are necessary for Raman spectroscopy. All throughout the world, laboratories use it to identify compounds, examine living cells without endangering them, and find illnesses like cancer.

Starts

On November 7, 1888, in the British Indian city of Trichinopoly, Madras Presidency, Chandrasekhara Venkata Raman was born. Located in the Indian state of Tamil Nadu, the city is today known as Tiruchirappalli.

Chandrasekaran Ramanathan Iyer, a maths and physics teacher, was Raman’s father. Parvathi Ammal, his mother, learned to read and write from her husband. The family didn’t have much money when Raman was born. Among the eight children, Raman was the second.

The Hindu caste of Brahmins, who are priests and scholars, included Raman’s family. Though Raman grew up with his father’s casual attitude towards religion, he did practice some Hindu rites and honoured cultural customs like vegetarianism. His father, on the other hand, paid little attention to religious things.

The family relocated to Waltair (now Visakhapatnam) when Raman’s father acquired a better job as a college lecturer when he was four years old.

Raman developed an early interest in science by reading the textbooks his father had used in school. He began taking out books on physics and mathematics from his father’s academic library as he became older. As he approached his adolescent years, his father, who had planned to pursue a master’s degree in physics, started teaching him from books he had purchased.
Starting a degree programme at the age of 14

At the tender age of 14, Raman left for the renowned metropolis of Madras, which is now Chennai, in 1903 to live in a dormitory and start Presidency College’s bachelor’s programme. Raman’s parents were troubled by his unwell appearance when he came home from his first year of college. His grandparents could take care of him at the Madras house they built up for him.

Raman had a great enthusiasm for science. He would show his younger siblings and sisters experiments when they were on vacation.

He earned awards in English and physics when he finished his degree in 1904. His British professors pushed him to pursue a master’s programme in the UK. Raman was encouraged to remain in India by Madras’s civil surgeon, who informed him that his health was not strong enough to survive the British environment.

This was probably very wise counsel. Born barely a year before Raman, the talented mathematician Srinivasa Ramanujan journeyed from Madras to work at the University of Cambridge in 1914. This hurt Ramanujan’s health even though it produced some amazing mathematics.
Nobel Laureate Mistakes 18-Year-Old Raman for a Physics Professor

Raman continued his master’s degree studies at Presidency College after receiving a scholarship. After his extraordinary potential was acknowledged, he was allowed unrestricted access to the laboratories, where he conducted research according to his ideas.

At the age of eighteen, Raman published his first scholarly paper in November 1906. When he had first given it to one of his lecturers, the teacher had not seemed to care. Raman sent his work straight to Philosophical Magazine, whereupon it was approved. It dealt with the behaviour of light and was titled Unsymmetrical diffraction-bands due to a rectangular aperture.

The distinguished British physicist Lord Rayleigh wrote to Raman after his second paper appeared in Philosophical Magazine. Rayleigh wrote to “Professor Raman,” not realising that Raman was only a teenage pupil.

At the age of 19, Raman received the highest honours for his master’s degree in physics in 1907 when he graduated.
Part-time scientist and full-time government administrator

Despite Raman’s desire to pursue a career in science, his brother convinced him to sit for the civil service examinations. Raman’s family was heavily indebted, and civil service employment paid well.

Raman was employed for ten years as a civil servant in the Indian Finance Department in Calcutta, which is now Kolkata. He advanced fast to a senior role in this department. He studied the physics of drums and stringed instruments in his spare time. At the Indian Association for the Cultivation of Science (IACS), he carried out this effort.

Before Raman discovered the IACS and started the process of bringing it back to life, it had been put into hibernation. Raman popularised science in Calcutta by giving public talks in addition to his research.

Eventually, Full-Time Science

Raman’s reputation as a highly-skilled physicist was cemented by his remarkable lectures and part-time research activity. He was approached by the University of Calcutta in 1917 when they extended an offer for the Palit Chair of Physics. Raman, who is now 28 years old, took the big pay drop even though it meant he could finally devote all of his time to science, which meant more to him than money.

Raman opted to teach lectures in addition to his research professorship since he was an engaging speaker and an inspiration to his students.

The Raman Effect
Raman and Rayleigh Scattering:

Lord Rayleigh, one of the greatest physicists of his day, had thought the teenage Raman’s publications were the work of a professor. He received the Nobel Prize in Physics in 1904.

The fact that Rayleigh was the first to explain why the sky is blue makes him significant to Raman’s tale. Then he explained that the colour of the sea was just a mirror of the colour of the sky.

During the summer of 1921, Raman found himself on a ship deck in the Mediterranean Sea while travelling to Oxford for the Congress of Universities of the British Empire. As he took in the stunning blue hue of the Mediterranean Sea, he started to question Rayleigh’s interpretation of its hue.

Rayleigh was right when he said that the reason the sky appears blue is due to a process that is currently known as Rayleigh scattering.

Anyone who chance to be around under such circumstances would see a black sky and a white sun if Earth had no atmosphere. But because sunlight interacts with the gases in Earth’s atmosphere, this is not what we see.

Sunlight is not reflected directly from the sun but rather is dispersed throughout the atmosphere. Since blue light is the most diffused and reaches our eyes from all directions in the sky, the sky appears blue. We typically see a yellow sun and occasionally a red sun because yellow and red light are the least scattered.

The scattering of Rayleigh is elastic. This indicates that when light photons contact with gas molecules, they do not lose any energy. As a result, the colour of the light remains constant.

Raman Learns that Light Is Scattering in the Sea

The unflappable scientist Raman took some basic physics equipment with him when he flew back to India in September 1921, including a prism, a small spectroscope, and a diffraction grating. Using these, he examined the sky and the sea, concluding that light was being scattered by the sea.

Rayleigh was therefore not entirely accurate when he claimed that the colour of the sea is only a reflection of the colour of the sky. Raman wrote a letter to the magazine Nature reporting his findings.

Upon his return to his lab, Raman and his pupils started a comprehensive study of light scattering.

Compton Presents an Inelastic Scattering Example

Exciting new research by Arthur Compton of St. Louis, Missouri, in 1923 revealed that X-rays can lose energy when they interact with electrons. After giving electrons a portion of their energy, the X-rays go on with less energy. Put differently, Compton established the possibility of inelastic scattering.

For this discovery, which led to the development of the Compton effect, Compton was awarded the 1927 Nobel Prize in Physics.

The Compton effect is significant because it dictates that X-ray and other electromagnetic radiation scattering must always be elastic in classical electrodynamics. Compton’s findings were consistent with quantum theory as opposed to classical theory.

Inelastic scattering by Compton led to a rise in X-ray wavelengths. Visible light would have a different colour if longer wavelengths and inelastic scattering were possible.
The Effect of Raman

Light scattering in gases, liquids, and solids was the subject of ongoing research by Raman and his pupils.

They discovered that a range of different liquids—sixty in total—did, alter the colour of the light when they employed monochromatic light, which is sunlight that has been filtered to leave only one colour. This was initially noticed in April 1923, albeit extremely sporadically.

They discovered a very noticeable colour shift in light scattered by glycerol, which was then known as glycerine, in 1927.

The effect was noted by Raman’s group in glass, crystals, and gases. The effect may have been confused with fluorescence, another phenomenon in which light changes colour; however, Raman’s work excluded fluorescence because the light dispersed by liquids in his experiment was polarised.

There had never before been observed what became known as the Raman effect, which is a colour shift accompanied by polarization. Fundamental to it all was inelastic scattering, which provided additional, powerful evidence in favour of quantum theory.

An Imprecise Illustration of the Raman Effect

When compared to Rayleigh scattering, the Raman impact is quite tiny. Seldom does one photon out of every ten million experience inelastic scattering.

In March 1928, Raman and his associate K.S. Krishnan published a report on their discovery in Nature.

For his “work on the scattering of light and the discovery of the effect named after him,” Raman was granted the 1930 Nobel Prize in Physics.

Raman Microscopy

Raman demonstrated that photon energy scattered inelastically acts as a “fingerprint” for the material from which the light is dispersed. Because of this, Raman spectroscopy is now often employed for compound identification in chemical laboratories across the globe. In addition, it is a non-invasive method of studying living cells and tissues in medicine, including the detection of cancer. Photons are produced by laser light instead of sunlight.

The Spin of the Photon

Raman and his pupil Suri Bhagavantam found in 1932 that photons, or units of light, have an angular momentum; in quantum terminology, photons have a spin feature.

Atoms that absorb electromagnetic radiation, such as light, get their angular momentum from the radiation.
A Few Personal Notes and the Conclusion

In 1907, Raman wed Lokasundari Ammal. Radhakrishnan, who went on to become a well-known astrophysicist, and Chandrasekhar were the couple’s two sons.

In 1929, Raman received a knighthood for discovering the Raman Effect, assuming the name Sir Chandrasekhara Venkata Raman.

Raman’s observations while at sea served as the original inspiration for his work, which won him the Nobel Prize. Interestingly, Subrahmanyan Chandrasekhar, another Indian Nobel laureate, completed most of his prize-winning work while at sea. Furthermore, it was even more ironic since Chandrasekhar’s uncle was C.V. Raman!