A thin film with index of refraction n = 1.42 is placed in one arm of a Michelson interferometer, perpendicular to the optical path. If this causes a shift of
9.0 fringes of the pattern produced by light of wavelength 556 nm, what is the film thickness? Answer in micrometers. Please help!

A thin film with index of refraction n 142 is placed in one arm of a Michelson interferometer perpendicular to the optical path If this causes a shift of 90 fri class=