Constructive and destructive interference of light waves is also the reason why thin films, such as soap bubbles, show colorful patterns. thickness: (a) Reflection Pattern: Let us consider a thin film of thickness t, refractive index µ and a ray AB of monochromatic light of λ is falling on it at an angle i. This phase change is important in the interference which occurs in thin films, the design of anti-reflection coatings, interference filters, and thin film … Note below that the reflection when traveling from air at n=1 to oil at n = 1.4 experiences the phase change, but from oil to water at n = 1.33 there is no phase change. Thin-film interference. Perhaps you have witnessed streaks of color on a car windshield shortly after it has been swiped by a windshield wiper or a squeegee at a gas station. If the thickness of the film is on the order of the wavelength of light, then colorful patterns can be obtained, as shown in the image on the right. Thin-film interference. The light reflected from any one Thin-film interference is the interference of light waves reflecting off the top surface of a film with the waves reflecting from the bottom surface. Figure 3.5.1 – Thin Film Destructive Interference In the figure above, part of the incoming wave reflects off the front surface of the transparent film (the red wave), and the rest of it is transmitted into the film, after which it reflects off the rear surface (the blue wave). When light hits a material that has multiple layers, each layer can reflect light. Thin Film Interference 12 n1 n2 n3 n1