Youve set up a Michelson interferometer with a helium-neon laser ( = 632.8 nm). After adjusting mirror

You’ve set up a Michelson interferometer with a helium-neon laser (λ = 632.8 nm). After adjusting mirror M₂ to produce a bright spot at the center of the pattern, you carefully move M₂ away from the beam splitter while counting 1200 new bright spots at the center. Then you put the laser away. Later another student wants to restore the interferometer to its starting condition, but he mistakenly sets up a hydrogen discharge lamp and uses the 656.5 nm emission from hydrogen atoms. He then counts 1200 new bright spots while slowly moving M₂ back toward the beam splitter. What is the net displacement of M₂ when he is done? Is M₂ now closer to or farther from the beam splitter?