A pre-set-up apparatus that produces an interference pattern as a result of the difference in two light paths. This can be related to the Michaelson-Morley experiment showing the lack of eather. The path length of one leg can be changed by ajusting a micrometer screw. A transparent material can be inserted in one leg to change the phase of the relfected light.
Question?
How far would one leg need to be lengthened to change the central region of the pattern from bright to dark?
