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Re: impedance of free space



A boo boo, Jack! The velocity of light is the square root of the
RECIPROCAL of the PRODUCT (not the square root of the ratio) of mu and
epsilon.

-Bob

Bob Sciamanda trebor@velocity.net
Dept of Physics
Edinboro Univ of PA http://www.velocity.net/~trebor
Edinboro, PA (814)838-7185
-----Original Message-----
From: JACK L. URETSKY (C) 1996; HEP DIV., ARGONNE NATIONAL LAB, ARGONNE,
IL 60439 <JLU@hep.anl.gov>
To: phys-l@atlantis.uwf.edu <phys-l@atlantis.uwf.edu>
Cc: JLU@hep.anl.gov <JLU@hep.anl.gov>
Date: Wednesday, April 22, 1998 8:27 PM
Subject: RE: impedance of free space


Hi Larry-
I think that the correct answer for an introductury course is this:
The constants K_e and K_m are determined by our choice of units for
electric and magnetic charge and our unit of length. The significant
fact
is that these two constants are related so that their ratio, regardless
of our
choice of units, is just the square of the speed of light. This fact
suggests
that light is somehow related to electricity and magnetism and electric
and
magnetic forces are somehow related to each other.
Regards,
Jack

************************************************************************
************************
Sorry if this is a stupid question, but I'm rusty on this and none of
the
H&R or Serway level books give me a good answer. My students asked, "If
free space is totally empty, why does it have impedance [of 377 ohms]?"
I
was about to answer that free space isn't really empty and launch into
something about a sea of virtual particles, but then I thought I'd
better
ask the list first.

Thanks in advance,
Larry