Splitting of a spectral line (see spectrum ) into two or more lines of different frequencies .
The effect occurs when the light source is placed in a magnetic field . It has helped identify the energy levels in atoms; it also provides a means of studying atomic nuclei and electron paramagnetic resonance (see magnetic resonance ) and is used in measuring the magnetic field of the Sun and other stars. It was discovered in 1896 by Pieter Zeeman (18651943); he shared the second Nobel Prize for Physics (1902) with Hendrik Antoon Lorentz , who had hypothesized that a magnetic field would affect the frequency of the light emitted.