National Science Day 2027

C.V. Raman and the discovery

Chandrasekhara Venkata Raman was an Indian physicist working at the Indian Association for the Cultivation of Science in Kolkata. In 1928, using sunlight and relatively simple equipment, he observed that a small fraction of light scattered by liquids emerged at different wavelengths. The shift in wavelength was specific to the molecules involved — a new form of spectroscopy was born.

Raman published the finding in February 1928 and was awarded the Nobel Prize in Physics just two years later in 1930 — one of the fastest Nobel Prize awards in history, reflecting how clearly the scientific community recognised the discovery's significance.

The Raman Effect works because photons occasionally exchange energy with a molecule's vibrational or rotational modes. The shift in photon energy equals the energy of the molecular vibration — which depends on bond types and strengths. See our chemical bonding guide for how bond energy and bond type determine vibrational frequencies.

Modern Raman spectroscopy

Raman's original experiment required sunlight and photographic plates. Modern Raman spectrometers use lasers and sensitive photodetectors, making the technique fast, portable and sensitive to trace amounts. Applications include:

• Forensics — identifying drugs, explosives and inks at crime scenes without destroying samples.
• Pharmaceuticals — confirming the chemical identity and purity of medicines without opening packaging.
• Art conservation — identifying pigments in paintings non-destructively.
• Cancer diagnosis — Raman spectroscopy can distinguish cancerous from healthy tissue during surgery.
• Space science — the Mars 2020 Perseverance rover carries a Raman spectrometer (SHERLOC) to search for organic molecules.

For how the James Webb Space Telescope uses related spectroscopic principles to identify molecules in distant atmospheres, see our JWST chemistry article.

Activity ideas for 28 February