I just got a book on evanescent waves, and it is focused on fiber optics,   
   circuit lithography, and the like.   
      
   But the question I wsnt to pose is, can the evanescent wave phenom be used in   
   a humdrum manner to make simple optics measurements? Can even a cave man do it?   
      
   Here is experiment #1: Take an acrylic rod, and "pipe" light into it in a   
   darkened room. When you touch it, light will "spill" out the rod around your   
   finger.    
      
   The first question is whether this is "evanescent." I think it is, but would   
   like any opinions.    
      
   Next, I would like an explanation as to why light "spills" out. Part of this   
   phenom is frustrated internal reflection, but the 'trigger' is evanescent, or   
   is it? Could it be explained by just a refractive index change that interrupts   
   TIR?    
   Yes, I know the physics demo is done with separate light paths, to emphasize   
   the E field evanescent nature, but is the evanescent phenom operative here   
   also?   
      
   Experiment #2: Years ago, I invented a light up sign that you see in   
   restaurants everywhere. (1) (I invented it independently in 1975, and not sure   
   if the invention was a lot of independent people - but that's not important.)   
      
   OK - Here's the physics question about these signs. The magic thing about them   
   is the letters "glow," you get net light output from the disturbance on the   
   surface. How is that happening? And here is a thought experiment: If you were   
   to mark on the    
   surface of the sign with a transparent marker, like a piece of parraffin,   
   would it glow? And more: If you were to mark with a white-board marker which   
   leaves little or no bulk material, just some dye, would it also glow? Finally,   
   it seems that roughing    
   the surface also makes it glow. This probably trivial scattering untelated to   
   "evanescent."   
      
   Finally finally - I'd be interested in hearing about attempts to use this   
   effect in non-fiber optic regimes, for measurement purposes. Mark Johnson in   
   his book describes light being piped into a falling stream of water inside a   
   reflective cavity, but    
   gives few details.   
      
   JB   
      
   1. The signs are lit from the edge (out of sight), and can be considered a   
   planar "light pipe." There is a black background to enhance the effect.   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)