Re: Polarization

[John Denker <jsd@AV8N.COM>]

Quoting Bernard Cleyet <anngeorg@PACBELL.NET>:

>  Aliquando bonus dormitat Hewitus

OK.

> (et Feynman)

Huh?  That's true as a general proposition, but why tar
RPF with this particular brush?  I don't recall him
saying anything about pickets or fences.
 -- I-34 (plus the last bit of I-33)
 -- III-11

> Easy correction:  the jump rope represents the magnetic com 'pon ent.

That seems like a trick, verging on a dirty trick, since
the interaction is basically electrical not magnetic.

A better correction would be to follow the example of
Feynman and introduce the concept in terms of _birefringence_.
Then you can't go wrong:  either the ordinary ray *or* the
extraordinary ray is aligned with the axis of your microscopic
'pickets' or whatever you want to call them.

==================

As a philosophical remark:  I don't see why people should ever
be "shocked" when this-or-that ball-and-stick model fails
to entirely capture the physics.  For example, chemists make
ball-and-stick models of molecules all the time ... these are
useful for some purposes, even though they are far from 100%
realistic.  They model the structure but not the function;
obviously they fail to _react_ with one another the way real
molecules do.

 -- Is it important for students to appreciate the range of
validity versus invalidity of a model?  Sure.
 -- Do students often overestimate or underestimate the
range?  Yes.
 -- Is it possible for teachers or textbook authors to
completely specify the range of validity for every model
that gets mentioned?  No.

===========

Some people may be thinking that the desired outcome is to
get to the point where polarization is described in terms
of vectors and polaroid sheets are described in terms of
projection matrices.  But remember:  equations are themselves
just a *model* of reality.  And in this case the equations
have problems, profound problems, widely-underappreciated
problems.  See next note.