A laser beam passes through a slit that is 2000 nm wide. In the interference pattern created on a distant screen, the angular position of the two first-order dark fringes is 12.0 ∘. The beam then is shone on a soap film (nfilm = 1.40) floating on water (nwater = 1.33).
What is the minimum film thickness that causes light reflected at normal incidence from the air-film interface to cancel light reflected at normal incidence from the film-water interface?
Express your answer with the appropriate units.
t = 74.6m