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If one of the outer mirrors on a Michelson interferometer was to be misaligned by a small angle of theta, what would be the shape of the interference pattern in the detector plane? What would happen to this pattern as the other mirror moves?

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You would see more fringes across the detection plane as the angled wavefront interferred with a slight phase difference across the plane.

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Thanks. What do you think would happen to this new pattern if the other mirror was to move as well? –  John Roberts Sep 21 '12 at 2:01
    
I'll give you a hint. It does matter which mirror is misaligned. –  placeholder Sep 21 '12 at 21:03
    
As far as the shape goes, I think that instead of circular fringes, straight parallel fringes will be observed, with separations determined by the angle of tilt of the mirrors. However, I'm still not too clear on the exact nature of that separation effect in regards to the independent movement of each mirror. –  John Roberts Sep 21 '12 at 22:52
    
Oops! Sorry the above comment should read "doesn't" NOT "does". Fat fingers. –  placeholder Sep 22 '12 at 0:46

Misaligning one of the end mirrors will produce a set of vertical or horizontal fringes at the detector plane (depending on the misalignment of the mirror).

The number of fringes is proportional to the misalignment angle of the mirror and inversely proportional to the wavelength of the light. When first setting up the alignment of the interferometer, this effect can be used by adjusting the alignment until the number of fringes is reduced.

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