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Re: POLARIZATION

Perhaps in our informal e-mail descriptions we just aren't communicating
very clearly. My problem was not with the handedness or corkscrew nature
of the circularly polarized light but with the idea that light became polarized
like this by following a corkscrew path through the crystal. The corkscrew
nature of polarized light is simply an artifact of vector addition. A
"partical" of light that emerges from a crystal with a certain polarization
does not rotate once it leaves the crystal. However, the next particle to
leave will be slightly rotated from the first, thus creating a corkscrew
pattern in space. As the circularly polarized light advances through an
isotropic medium the corkscrew does not turn, it simply advances.
While the circularly polarized light has a handedness optically active
crystals need not have a handedness in their crystal structure.
One can produce other handed circularly polarized light simply by changing
the angle of incidence of the linearly polarized light incident on the 1/4
wave plate. It is not necessary to change the 1/4 wave plate. Circularly
polarized light is simply the result of interference caused by phase
differences.
on Fri, 05 Jun 1998 16:18:36 -0500 brian whatcott said:
David seemingly had some difficulty with my classification of 'left hand'
and right hand' polarizations of EM waves.
Nevertheless, that's how it is!

And at below VHF on up through light frequencies, it is quite rational to
describe a circular ( properly helical) polarization as a quarter wave
displacement of orthogonal components, as he does.

But perhaps David has forgotten that the sense of the quarter wave
displacement (advanced or retarded) determines the handedness of such
electromagnetic waves.

Brian Whatcott Altus OK


At 15:18 6/4/98 EDT, David wrote:
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. ...

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 conformational 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.
...
Brian Whatcott Altus OK