You illuminate a michelson interferometer with a helium-neon laser. the interference pattern is uniform – there are no stripes or rings. the laser has a wavelength of 632.8 nm. you move the mirror on the translation stage until the intensity of the interferometer output is maximum. you measure that the output intensity is i0 = 0.80 mw/cm2. then, you move the mirror on the translation stage by some additional amount \deltax. you observe that the output intensity drops monotonically to 0.63 mw/cm2 . what was the value of \deltax? (note the specification that the intensity falls monotonically means that the intensity never went to zero during your additional mirror displacement.)