Jamin interferometer
The Jamin interferometer is an interferometer invented by Jules Célestin Jamin in 1856 . It allows the measurement of changes in the refractive index of gases and liquids.
construction
The interferometer consists of two thick glass panes mirrored on one side. The two panes are offset in parallel and set up in opposite directions. The non-reflective side acts as a beam splitter . Incoming light is split into two parts by the front of the first mirror. One of the components is reflected on the front. The other part goes into the glass. It is reflected on the back of the glass and mostly emerges from the glass at a point slightly offset from the first ray.
The two parts run through the distance between the two panes of glass. The front of the second mirror acts as a beam splitter and superimposes portions of the two beams generated by the first pane of glass. The roles of the two beams are reversed. There the first beam passes through the pane of glass, while the second beam is partly reflected directly.
If the surfaces of the two glass panes are ground exactly parallel and the two panes are arranged exactly parallel, then both optical paths are the same length. Under these circumstances, constructive interference occurs at the exit of the interferometer . This means that the intensity of the light emitted is maximum. If, on the other hand, the optical paths differ by half a wavelength, then the intensity of the emerging light is minimal. This variation in intensity can be observed comparatively easily.
Measurements of changes in the index of refraction
The interference pattern that appears at the output of the interferometer depends sensitively on the relative optical length of the two light paths. This fact can be used to determine the influence of pressure on the refractive index of a sample. For this purpose, a pressure chamber filled with gas or liquid and equipped with windows is introduced into one of the two light paths of the interferometer. A change in the pressure in the chamber changes the optical length of this part of the interferometer. For each wavelength that makes up this change, the intensity at the output goes through a pass from maximum to minimum.
Individual evidence
- ↑ Jules Célestin Jamin: New Interferential Refractor . In: Annals of Physics and Chemistry . tape 174 , no. 6 , 1856, pp. 345-349 , doi : 10.1002 / andp.18561740619 .
- ↑ Jules Célestin Jamin: Description d′un nouvel appareil de recherches, fondé sur les interférences . In: Comptes rendus hebdomadaires des séances de l'Académie des sciences . tape 42 , 1856, pp. 482 ( digitized on Gallica ).