1. The problem statement, all variables and given/known data The distance between the movable mirror and the beam splitter in a Michelson interferometer is increased a small amount. When this happens, you see 200 dark fringes move across the field of view. If the incident light was 600nm, by how much was the mirror moved (in millimeters)? 2. Relevant equations ? 3. The attempt at a solution My teacher has not taught me anything about Michelson interferometer. It not even in the book! I asked my tutor and he does not know how to solve the problem. He knew about Michelson but he doesn't know how to link it together to solve the problem.