Search Here

TODAY IN HISTORY - 28 FEBRUARY




• 1928 C. V. Raman discovers Raman scattering (also known as Raman Effect).

Raman scattering or the Raman effect is the inelastic scattering of a photon. It was discovered by C. V. Raman and K. S. Krishnan in liquids, and by G. Landsberg and L. I. Mandelstam in crystals. The effect had been predicted theoretically by Adolf Smekal in 1923.

When photons are scattered from an atom or molecule, most photons are elastically scattered (Rayleigh scattering), such that the scattered photons have the same energy (frequency and wavelength) as the incident photons. A small fraction of the scattered photons (approximately 1 in 10 million) are scattered by an excitation, with the scattered photons having a frequency different from, and usually lower than, that of the incident photons. In a gas, Raman scattering can occur with a change in energy of a molecule due to a transition to another (usually higher) energy level. Chemists are primarily concerned with the transitional Raman effect.

• 1953 - Scientists James D. Watson and Francis H.C. Crick announced they had discovered the double-helix structure of DNA, the molecule that contains the human genes, at Cambridge University.

• 1991 – The first Gulf War ends.

• World Tailors Day

World Tailors Day is an annual day observed on February 28 by tailors in several countries.  The date of observance it is the birthday of Sir William Elias Howe, inventor of the sewing machine by using the lock stitch loop method in the year 1845.





Related Posts Plugin for WordPress, Blogger...