Final answer:
Thin film interference is the formation of a whitish haze film on the surface of a coating. It occurs when light interacts with a thin film having a thickness smaller than a few times the wavelength of light.
Step-by-step explanation:
Formation of a whitish haze film on the surface of a coating is known as thin film interference. The bright colors seen in an oil slick floating on water or in a sunlit soap bubble are caused by interference between light reflected from different surfaces of a thin film.
When light interacts with a thin film having a thickness smaller than a few times the wavelength of light, different colors can be observed due to the interference effects.