Re: The biggest mistake in classical optics


"Timo A. Nieminen" <timo@xxxxxxxxxxxxxxxxx> schrieb im Newsbeitrag
news:Pine.WNT.4.64.0606262112530.1388@xxxxxxxxxxxx
On Fri, 22 Jun 2006, Edward Green wrote:

Given the finite wavelength of light, it
can't really make any difference if we interpose a infinitesmal vacuum
layer or not, can it?

No.

Yes it can


Take an interface between two media, calculate reflection and transmission
coefficients (either amplitude or power, your choice), and then take 3
media, and ditto. Take the limit as the thickness of the middle medium
approaches zero, and you get the 2 media case.

For example, if it's a high-index layer between 2 identical media, then
there's a 1/2 wave phase shift between the reflections from the front and
back of the interface, and these destructively interfere as the thickness
-> 0. In the limit, no reflection; the middle medium becomes completely
transparent. This is even the case when you have total internal reflection
- tunnelling across a 0 thickness barrier gives 100% transmission.

Haven't read the original post in detail, but IME there is no problem, if
you do it properly. Do it wrongly, and it's easy to get the wrong result,
especially when dealing with lossy or gain media. Don't talk about angles,
talk about wavevectors instead.

--
Timo Nieminen - Home page: http://www.physics.uq.edu.au/people/nieminen/
E-prints: http://eprint.uq.edu.au/view/person/Nieminen,_Timo_A..html
Shrine to Spirits: http://www.users.bigpond.com/timo_nieminen/spirits.html



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