Thin Film Interference Use Polarizing Film & Plastic Wrap

Stolen (on short notice) from Wikipedia.com: Oil film, Soap Bubbles, or plastic “film”: Light incident on an oil film. Air is at the upper boundary and water at the lower boundary. In the case of a thin oil (etc.) film, a layer of oil sits atop a layer of water. The oil may have an index of refraction near 1.5 and the water has an index of As in the case of the soap bubble, the materials on either side of the oil film (air and water) both have refractive indices that are less than the index of the film. Or n air n water. The equations for interference will be the same. 2n film d cos θ 2 = (m – ½) λ for constructive interference of reflected light. 2n film d cos θ 2 = m λ for destructive interference of reflected light.