Demonstrating Fourier transform spectroscopy for students.

A Michelson interferometer with 230-mm mirror displacement is used to study coherence length and line shape of several light sources in the visible range. The instrument's construction is simple. Using quasimonochromatic symmetric spectral lines, a method is described for obtaining information about the source line shape from the envelope of the interferogram. Doppler-and pressure-broadened lines can easily be distinguished. The instrument gives a good demonstration of the Fourier relation of interferogram and spectrum.