Ok, here we go. I'm doing my PhD on a thing called surface plasmon resonance, which involves surface plasmons being excited in an evanescent field. (lost you yet?) Here is a link to a book that Im looking at for a more in depth explanation of the evanescent wave/field:

http://tiny.cc/z7Qo9

Looking on page 16 2.2 the evanescent wave: line three, is says "this is conveniently done by considering the phenomenon of total internal reflection."
That's fine and I understand that but on page 17 figure 2.1 the diagram shows refracted light which is in place to explain the various equations.
I'm completely confused why the figure is used, how can you explain the evanescent wave being induce when light under goes total internal reflection with a diagram of refracted light? It may help that n2 is a thin gold layer.
I have spoken to some optics guys in the uni and they are confused too. Can anyone explain it to me?

The diagram is just there to make clear the labelling of angles, wave vector components etc. as used in the text.

Total internal reflection is a special case of refraction. To derive the formulae for internal reflection you start with refraction, and then show the existence of the critical angle, which is what they do in the text. So it makes sense to define variables that way – it's just confusing they put the diagram near the end of that section of text instead of at the top, as if it showed the result of their derivation rather than the starting point.

Ok, thanks. I wish people would be a lot more clearer when writing books!

Just googled to find out some more about your field, looks like some rather cool stuff at an interesting stage of development…

Yeah I get to play with lasers for a living and have a gadget named after me! The EMMA-excited multiple microbial array! How cool!