Hello all, I have recently encountered a problem in my understanding of how evanescent waves work. The problem will refer to the diagram found at http://www.popularscience.co.uk/features/nimtz2.jpg (while the evanescent wave isn't drawn this is the only example i could find). So physically light enters the prism and is reflected back due to the incident angle being greater than the critical angle. Due to the boundary conditions put forward by Maxwell the parallel component of the electric field at the interface must be zero. This gives rise to a decaying electric field. First question : what is this decaying field physically? surface vibrations of electrons? This decaying field is then intercepted by a second prism and then light is seen to be emitted from the second prism. Second question : What physically causes these photons? the evanescent field interacting with electrons at the second interface causing emission of light? I understand that my confusion comes from a lack of understanding of an evanescent field probably. Though I would be happy with that if I hadn't already learned quantum tunneling as an undergraduate!! (an analogy to this problem) Thanks for any help you can give in interpreting equations into a physical meaning my brain can comprehend!