The 1952 Nobel Prize for Physics was shared by physicists Felix Bloch and Edward Mills Purcell for their independent discovery of nuclear magnetic resonance. In nuclear magnetic resonance spectroscopy, a substance to be analyzed is exposed to electromagnetic radiation under controlled conditions in a magnetic field. Selected wavelengths of radiation will be absorbed by the substance depending on its chemical composition. The absorption spectrum of the material indicates the wavelengths that have been absorbed, enabling researchers to determine the molecular structure of the substance.