Main Page | See live article | Alphabetical index In optics, evanescent waves are formed when sinusoidal wavess are (internally) reflected off an interface at an angle greater than the critical angle so that total internal reflection occurs. "Evanescent" means "tending to vanish", which is appropriate because the intensity of evanescent waves decays exponentially (rather than sinusoidally) with distance from the interface at which they are formed. Source: http://www.andrew.cmu.edu/user/dcprieve/Evanescent%20waves.htm This article is from Wikipedia. All text is available under the terms of the GNU Free Documentation License.