K.S. Krishnan: The Physicist Behind the Raman Effect

K. S. Krishnan was an Indian physicist. He studied light and magnetism. Most people know him as Raman’s closest partner.

Where did he start?

• He was born in 1898 in Watrap, a village in South India.
• He studied at the American College in Madura and Christian College in Madras.
• He then studied at the College of Science, Calcutta University.
• He reached Calcutta in July 1920 to work with C. V. Raman.
• Madras University gave him his master’s and doctorate for his research.

When did he die?

He died in New Delhi on 14 June 1961. The cause was a heart attack.

What is the memory hook?

Think “1898 born, 1920 met Raman, 1961 gone”. Raman was his guru.

The Raman effect is a change in the colour of scattered light. Most scattered light keeps its colour. A small part changes. That small part is the Raman effect.

How did it begin?

• In 1923 Raman’s student Ramanathan saw a faint change in scattered light.
• Nobody followed it up at the time.
• On 7 February 1928 Krishnan saw the same effect in liquids.
• In December 1927 Arthur Compton had won the Nobel Prize for his X-ray effect.
• Raman then said light must show a similar effect.

Why is 28 February special?

• 28 February 1928 is taken as the official date of the discovery.
• India marks it every year as National Science Day.
• The first National Science Day was in 1987.

What is the memory hook?

Think “Compton for X-rays, Raman for light”. The date 28 February became the national day.

Krishnan was the one doing the experiments. His diary of February 1928 shows how closely the two worked together.

What does the diary say?

• The diary covers only 5 to 28 February 1928.
• On 9 February Raman said the effect should be called the Raman-Krishnan effect.
• The first paper went to Nature on 16 February 1928.
• Raman and Krishnan wrote it together.
• A third joint letter followed on 22 March 1928.

What did Raman say in private?

A student later recalled Raman saying Krishnan deserved half the credit. Raman added that he would share any reward with Krishnan.

What is the memory hook?

Think “two names on the paper”. The first letter to Nature had both names.

The 1930 Nobel Prize in Physics went to Raman alone. Krishnan was not named in the award.

What happened?

• The prize was announced for the discovery of the Raman effect.
• The review says Raman later began to project himself as the sole discoverer.
• It says he asked Rutherford and Bohr to nominate him for the 1929 prize.
• Krishnan never complained in public.
• He stayed loyal to Raman all his life.

Is the story settled?

Not fully. The diary is incomplete, and records from March to April 1928 are missing. Writers still debate how credit should be shared.

What is the memory hook?

Think “one prize, one name”. The credit question is still debated.

After 1928 Krishnan moved away from the Raman effect. He studied magnetism in crystals.

What was his career path?

• 1928 to 1933: Reader in physics at Dacca University.
• 1933: Mahendralal Sircar Professor at the Indian Association for the Cultivation of Science, Calcutta.
• 1942: Professor and head of physics at Allahabad University.
• Late 1940s: first Director of the National Physical Laboratory (NPL), New Delhi.

Which date is right for NPL?

• The Physics Today obituary says 1947.
• The 2012 book review says April 1948.
• Exams usually ask only that he was the first Director.

What else did he do?

• He worked on magnetism in crystals.
• The review says he began the first cryogenic research in India.
• He sat on India’s Atomic Energy Commission.

What is the memory hook?

Think “Dacca, Calcutta, Allahabad, Delhi”. Four cities, four posts.

Krishnan got many honours at home and abroad. He kept his life simple.

What are the main ones?

• He was knighted in 1946.
• He was a Fellow of the Royal Society.
• He won the Bhatnagar Memorial Award.
• He served as president of the Indian Science Congress.
• He won the Liege University Medal.

What did he refuse?

After S. S. Bhatnagar died in 1955, Krishnan was invited to head CSIR. He refused. He wanted time for research.

What is the memory hook?

Think “knight, fellow, but still a lab man”. He chose research over office.

Four mix-ups come up again and again. Learn each pair.

What are the traps?

• Who won the Nobel? C. V. Raman won in 1930. Krishnan did not.
• Which date? 28 February 1928 is the discovery date and National Science Day.
• Which Krishnan? K. S. Krishnan worked with Raman. R. S. Krishnan is a different physicist.
• First at what? Krishnan was the first Director of NPL.

How do you remember them?

Think “Raman won, Krishnan helped”. Then recall “28 February”.