... the oxide film surface simultaneously reflection and refraction. The light 2 is refracted into the oxide film on the surface of ... wavelength is λ, when the optical path difference is δ = kλ + λ / 2 (k = 0, 1, 2, 3, ...), the optical vibration is weakened. White is ... , purple gradually change, the wavelength becomes shorter. From the formula (2) shows, in theory, at an appropriate angle, with the oxide ...