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Re: POLARIZATION



You are making circular polarization much more complicated than it really is.
Let me quote from An Introduction to the Methods of optical Crystallography by
Donald Bloss. "If the path difference between the two waves emergent from a
crystal is lambda/4 (or any odd multiple of lamda/4) their vibrations interfere
where they coincide in space and time, to produce resultant vibration vectors
of constant lengths but variable azimuths..." There is no need to invoke
handedness or corkscrew paths. All that is needed is an asymetic crystal
structure for which the velocity depends on the plane of polarization.
Actually, the majority of natural crystals exhibit this optical activity.
Do not confuse the corkscrew description of circularly polarized light with
what is going on within the crystal. This description applys once the light
leaves the anisotropic crystal and is in an isotropic material (like air)
Within the crystal you have two waves with planes of polarization perpendicular
to each other. Circular Polarization results when these two waves are combined
(vectorially). Note that path differences other than integer multiples of
lamda/4 will produce elliptical polarization.

On Fri, 29 May 1998 10:09:12 -0500 brian whatcott said:
It is not difficult to configure an array of dipoles, yagi style, so that
the polarization angle is changed. Just a matter of geometry of conductors.

In stereo chemistry, stereoactive materials are classified as
configurational, geometric and confirmational isomers which involve either
chirality (handedness, or non superimposability of a mirror-image) or
rotation of some part of a molecule round a double or single bond.

Achnowleging that at some level this optical activity has to be described
by the angles of charge motion, I still find no great difficulty in
accepting some mechanism of this kind.

I fancy Ludwik finds a solid crystal array a more challenging object for
didactic description. One would hope that adjacent bonds are disposed at
angles which provide a natural 'corkscrew' path through the material (i.e.
a natural progression of charge carrier angle of oscillation) - though I
expect there is more than one mechanism for providing a preferential angle
of transmission through adjacent layers.

Perhaps I am too easily pleased, but these details are essentially just
'engineering' of the natural kind, to my way of thinking....

Brian Whatcott Altus OK