Re: [Phys-l] g & E fields

[Brian Whatcott <betwys1@sbcglobal.net>]

Interesting to see an input from a physics list  on human sensory
 capabilities.
Reminds me of the question that  sometimes arises here:
 if one expends energy even when stationary
(say one is pushing against a wall) then  a Newtonian modeler
 may well ask:    How can this be?

About the constant intensity of helical em waves:
 helical  (circularly  polarized) em waves can of course be
synthesized from two orthogonally polarized em waves.

Because such waves would be phase displaced to provide the wave
rotation, then the possibility that their instantaneous amplitude
 squared  value does not vanish, is easy to accept.

  As usual, there is a clear comparison
 with lower frequency em waves: where the antennas in question
may be  launched by a helical wire, or by spatially displaced and
orthogonal dipoles.

I noticed an important concept arose in this thread: the assertion
 that the e wave and the m wave are either phase displaced or
in phase but orthogonal (as described by different writers here.)

The source of some confusion  in this area is probably the exchange
of energy  between  L and C in a resonant circuit, or between
various other  energy stores in other kinds of resonators so that the
m energy store is out of phase with the e energy store.

It is plausible to imagine the first wave being driven into a dipole,
so that current is maximal near the center whie the maximal e wave
 bridges the ends after a (phase) delay.
   This seems to speak against the phase identity of e and m components
emanating from this simple conceptuial model antenna. Strange....


Brian W

At 04:01 PM 1/7/2008, you wrote:
> From: WC Maddox
>
> The human eye/brain cannot detect light variations on the time scale
> of one period of a light wave. The intensity we observe is determined
> by the average value of the Poynting vector. For a sine wave type
> variation of electric field the average is proportional to 1/2 of
> square of E(max). For two waves of equal amplitude and in phase,
> E(max) = 2 x E(peak of one wave). See Sears and Zemansky for further details.
>
> End Message
>
>
>
>
>
>
>
> At 08:27 PM 1/6/2008, you wrote:
> >At 08:02 PM 12/3/2007, you wrote:
> >
> > >Here is another tricky question on the energy of the electromagnetic
> > >wave: Is the intensity of the bright fringe (For example, Young's
> > >Double Slit Experiment) always the same when the electromagnetic field
> > >is varying? Neither is this question easy to be explained too.
> > >
> > >
>
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Brian Whatcott    Altus OK    Eureka!