Raman effect in Physica
Sir Chandrasekhar Venkat Raman (he was knighted for this discovery), propounded a new theory on scattering of light. Subsequently he won the Nobel Prize for physics in 1930.
Raman after intensive study at his laboratory in Bangalore concluded, that when a light beam travels through a medium, the beam is deflected by the molecules. But more important he observed that a small part of the emerging light beam after deflection by the molecules had a different wave length from the original beam. In other words the wavelength of light after passing through a medium and being deflected by the molecules had a different wavelength.
This change in wavelength of the light beam is known as the Raman Effect and forms an important part of spectroscopy. The limiting factor for this was that the light had to pass from a dust free medium. He also observed that the entire beam did not have its wavelength changed, but only a small part.As can be seen the incident light after deflection by the molecules is scattered. Some parts of this scattered light have a different wavelength from the original beam.
The original beam may consist of particles or photons. This beam will have a frequency and on striking a surface it gets scattered. Frequency changes were observed by Raman in some parts of the scattered light.The science that deals with this change of frequency is referred to as Raman spectroscopy. This discovery at that time appeared of not much use, but now the Raman Effect has tremendous use in a variety of fields.Generally it is seen that the Raman Effect is feeble in liquids, but it is feebler in gases. Hence the Raman Effect is studied in liquids and solids. Gases have low molecular concentration and scattering of light is dependent on striking molecules. The Raman Effect is low in gaseous medium.
A development is the hand held scanners called Raman scanners, which weigh just about 300gms. These are used by US narcotics squads and airports to detect drugs. Security experts have concluded that Raman Scanners can also be used to detect explosives being carried by terrorists. Safety inspectors are already using Raman scanners to detect hazardous chemicals and gases. It is also finding use in forensic work.
