The wavelength of an He-Ne laser is determined from the change in the
interference pattern when moving an interferometer mirror using the
shifting distance d of the mirror. During this shift, the interference
lines on the observation screen move. In evaluation, either the interference
maxima of interference minimum passing a fixed point on the screen while
the plane mirror is shifted are counted. For the wavelength, the following
1. Rotating the knurled head screws X1 and X2 to
bring two beams coincide.