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Suppose a laser beam is split into two beams which interfere and show an interference pattern on a screen, as in the Michelson interferometer.
If the length of one beam is shortened by an eighth of a wavelength and the other beam is lengthened to the same degree (a quarter of a wavelength total offset), will an observable fringe shift or any other change occur in the fringe pattern?
Would you know of a reference where the answer to this question has been experimentally verified?
Thank you very much,
- Boris Milvich (age 42)
Sure, you'll see a shift in the fringes. This is an experiment we often do as a lecture demonstration. You can either shift the fringes by slightly moving one mirror with a fine-threaded screw or by letting air in or out of a chamber in one of the pathways. The air deosn't change the pathlength but it does change the wavelength, which has the same effect. Usually, we don't like to think of this site as a reference source, because we're just relaying say-so. Since this is one experiment we've done ourselves, I guess you could consider us the reference. A bit of Googling should turn up others.
(published on 02/22/2008)
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