Talk:Evanescent field

not clear from explanation why kz is larger than k when total internal reflection occurs.

It does gloss over that. Basically, if you solve the problem of matching the incident, reflected, and refracted waves at the boundaries, you find they all must have the form

$\mathbf {E} (y=0)=\mathbf {E} _{0}e^{-ik_{z}z}$

But we also know from Snell's law that

$n_{1}\sin \theta _{incident}=n_{2}{\frac {k_{z}}{|\mathbf {k} _{refracted}|}}$

When that $\sin \theta _{incident}$ on the left equals $n_{2}/n_{1}$, $k_{z}=|\mathbf {k} _{refracted}|$. For $n_{1}>n_{2}$, at larger incident angles, $k_{z}$ is bigger than $|\mathbf {k} _{refracted}|.$

Practical Applications

See this spectrum article.

References

Could someone please add references to the electric section? Sorry - I don't know how to tag it as needing references. 137.215.6.53 (talk) 07:40, 18 July 2008 (UTC)

direction of evanescence

Isn't this page lacking the information (or at least needing to put it more clearly) that the direction of the evanescent electric field is the same of the exponential decaying? I have the impression sometimes that people care much about the fact that the evanescent waves "evanesce" exponentially, but this is by no means its most notable characteristic. The fact that the field is in the same direction of this decay is the one worth noting. -- NIC1138 (talk) 05:18, 13 January 2009 (UTC)

Correct me if I'm wrong. My understanding of evanescent waves is that they are already by nature "directional." It would follow that the exponential decay is also directional. Pointing it out, seems to me to be akin to saying "The sky is blue, but it is not black." The last half of the sentence is unnecessary. Simple logic should lead the reader to infer the decay is in the same direction IMHO.

merger proposal

As the separate page on "evanescent wave coupling" is quite short, and concentrates on practical applications, it seems to me that it would be better to merge it into this page. Is anybody opposed to this idea ? (RGForbes (talk) 21:43, 11 March 2009 (UTC)).

A merged article would probably have a more consolidated content.-Thurth (talk) 06:54, 9 April 2009 (UTC)

Possible addition/correction

I found this article while preparing an exam in photonics and I think a correction might be necessary. My understanding is that an evanescent wave appears when a wave crosses from a denser to a thinner material, in my case optically denser/thinner. This is one of the prerequisites for total reflection, which is connected to the appearance of evanescent waves. Is this true for any electromagnetic wave? Everything I've read seems to imply so, however I'm rather a layman in the field so I'd like to be sure :)

Longbowman3 (talk) 13:57, 16 April 2009 (UTC)