Avery thin oil film (noil = 1.25) floats on water (nwater = 1.33). what is the thinnest film that produces a strong reflection for green light with a wavelength of 500 nm? as light travels from air into the water through the oil film, both of the reflected waves undergo a phase change. neither of the reflected waves undergoes a phase change. only one of the reflected waves undergoes a phase change.