© Science Museum / Science & Society Picture Library
The Toronto Arc provides a light source for Raman spectroscopy. The 'Raman Effect' is a change of wavelength exhibited by some of the radiation scattered by molecules and ions used in spectroscopic analysis. It was named after Chandrasekhara Venkata Raman (1888-1970), the Indian physicist who discovered it, and led to one of the earliest confirmations of quantum theory; that energy does not have a continous range of values. Instead it is radiated (absorbed) discontinuously in multiples of indivisible units called quanta.