[SI-LIST] Re: (no subject)
- From: "Tabatchnick, Justin" <justin.tabatchnick@xxxxxxxxx>
- To: <si-list@xxxxxxxxxxxxx>
- Date: Tue, 10 Dec 2002 17:20:02 -0800
Hi Sandor;
I beg to differ - I don't know who wrote the article but they are wrong =
- They mention that the dielectric constant varies with frequency - is =
it a linear or nonlinear variation - I don't think they even know =
because they are wrong -are you telling me that the wavelenth does not =
change in a medium that it is the dielectric constant or are you saying =
that the frequency changes with the dielectric constant - think of this =
- if the frequency changes at the medium interface , it goes from higher =
to lower or reverse then at the interface there is a discontinuity that =
can not be imagined. I have better analogy let's discount any losses, =
energy equals plank's constant times the frequency . Energy conservation =
dictates that the energy crossing a boundry will be the same on both =
sides in a lossless medium which means the frequency has to remain =
constant.
Justin
-----Original Message-----
From: Sandor [mailto:sandor@xxxxxxxxxx]
Sent: Tuesday, December 10, 2002 4:58 PM
To: si-list@xxxxxxxxxxxxx
Cc: justin.tabatchnick@xxxxxxxxx
Subject: RE: [SI-LIST] Re: (no subject)
Justin wrote:
> I have to jump in to add my 2 cents for all it's worth. First=20
> of all the =3D
> realative dielectric constant is not frequency dependent
I must protest! ;-)
Relative dielectric constant is a bit of a misnomer, it is really a=20
variable (except in vacuum where it is always 1, but vacuum is a very=20
homogenous "medium").=20
> - you can =3D
> explain light dispersion not by a variation of dielectic with=20
> frequency =3D
> but a variation of speed in the medium with the relative dielectric =
=3D
> constant . Velocity =3D3D frequency times wavelength ,=20
> wavelength is equal =3D
> to the wavelength divided by the square root of the relative=20
> dielectric =3D
> constant- white light is made up of a spectrum of varying=20
> wavelengths =3D
> all traveling at the same speed in air however in a medium=20
> their speeds =3D
> differ and that is why you see a seperation.
Maybe I'm not reading this the way it was intended, but the above=20
explanation appears to be a "tail wagging the dog" type of argument and=20
seems to suggest that different frequencies travel at different speeds=20
because of their different wavelengths rather than because of the=20
freqency variability of Er.
Their speed differs precisely because of the freq dependency of Er.
There are plenty of related stuff on the net, just one example...
http://chsfpc5.chem.ncsu.edu/CH795Z/lecture/lecture7/refl_refr/reflection=
_refraction.html
> the only way you will see a =3D
> variation in the dielectric constant is in a non-homogenous=20
> medium. On =3D
> the other hand if a medium has any conductivity to it you will see a=20
=3D
> variation with the loss tangent with frequency.
???
Regards,
Sandor
---
------------------------------------------------------------------
Sandor Daranyi
Senior Design Engineer
Aristocrat Technologies Australia Pty Limited
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