Reflected light micrograph of thinfilm Interference on a soap bubble. The colours on the surface of a soap bubble are the result of light waves being refracted, or bent, as they pass through the thin film of soap solution that makes up the bubble. The process is called thin film interference. When light waves pass through a thin film, they bounce off the front and back surfaces of the film and interfere with one another, creating a pattern of light and dark areas known as interference fringes. The colours change in response to the observation angle and as the thickness of the skin of the bubble changes.