A system based on the Mach--Zender interferometer is described. It can be used for lecture demonstrations of interference between light waves with adjustable statistical parameters (degree and time of coherence). The light source is a continuously operating gas laser. Partially coherent light can be produced by modulating with one of the mirrors, using a piezoelectric barium titanate cylinder to establish the required amplitude and frequency. Another method used to vary the degree of coherence continuously from 1 to 0 relies on the introduction of a second, similar laser beam. More accurate quantitative data can be obtained by using a scanning mirror in conjunction with a photomultiplier. This transforms the intensity distribution into a ``transverse'' pattern on the screen of an oscilloscope. Polarization effects can also be demonstrated.

@article{Egorov:1979,
	author = {G. S. Egorov and S. N. Mensov and N. S. Stepanov},
	title = {Lecture demonstrations on the interference of partially coherent light},
	publisher = {Physics-Uspekhi},
	year = {1979},
	journal = {Phys. Usp.},
	volume = {22},
	number = {9},
	pages = {757-759},
	url = {https://ufn.ru/en/articles/1979/9/e/},
	doi = {10.1070/PU1979v022n09ABEH005610}
}