Lummer–Gehrcke interferometer
MULTIPLE-BEAM INTERFEROMETER
Lummer-Gehrcke interferometer; Lummer–Gehrcke plate; Lummer-Gehrcke plate
The Lummer–Gehrcke interferometer or Lummer–Gehrcke plate is a multiple-beam interferometer similar to the Fabry–Pérot etalon, but using light at a steep angle of incidence. The interferometer consists of a long plate of glass or quartz, with faces that are polished accurately flat and parallel.