Re: What is frequency??


Sue... wrote:
PD wrote:
Sue... wrote:
PD wrote:

Now, please refer to what I said earlier. In *every single instance* of
a transverse wave propagated along a medium like a string, the velocity
of the propagation is related to two things: the elastic modulus
(stiffness) of the medium and the inertia of the medium. Both of those
quantities are independently measurable. This is how we know this rule
applies to all transverse waves propagated along a medium. For example,
for a guitar string, we can measure the elastic modulus of the material
of the string in an experiment that has nothing to do with waves, and
we can measure the inertia of the material of the string, and we can
use that to *predict* the velocity of the wave in the guitar string and
then compare that with a direct measurement of that wave speed -- and
it works. In fact, we can go the other way and by measuring the
velocity of the wave speed, we can predict either the elastic modulus
of the string material or the inertia of the string material, and then
compare that with the independent measurements of either of those --
and it works. I repeat -- this doesn't work only for guitar strings; it
works for every single case of a transverse wave supported by a medium.

Now, here's the rub. When you try to do that with a presumed medium in
otherwise empty space and try to figure out what values for elastic
modulus or inertia would be appropriate from a propagation speed of c
this necessarily implies either a value of stiffness or a value of
inertia that is obviously ridiculous.

An electromagnetic medium always has an opposite charge
moving in the opposite direction in response to incident light
so these kinds of mechanical continuum argurments don't apply.

Really? Where is the charge moving in the region between here and the
sun?

Most of them are orbiting hydrogen nuclei.
http://www-ssg.sr.unh.edu/ism/what1.html

The density of hydrogen nuclei in the ISM is about 1 per cubic cm. So
how does light get from one atom to another that's 100,000,000 atomic
diameters away?


The charges at either end of the path are of course
always there or you have no path.



Coulomb force and electron mass nicely accounts
for the speed of light just as mass and tension of
a musical instrument string.

<<Nice pseudo-dense babbling.>>
Harumph!
Please show where the coulomb force and the electron mass appear in an
equation for the speed of light in a manner analogous to the equivalent
terms for the case of a musical string.
Because Coulomb force and string tension have an inverse relation
to distance, It doesn't get much closer than what you see in the
NIST equation. It might be helpful if you look at some expressions
for permittivty and imagine how the equation would change if you
substitue a spring for the Coulomb coupling.

Don't make me squint to try to see it.
Do it. Show it.


Your links below do not make it obvious -- perhaps you could be more
specific.

The below doesn't help.
If there's something in there you see, show it.


<< The key to the electron mass is, perhaps surprisingly, the
definition of the Rydberg constant from atomic spectroscopy:
R¥ = a2mec/2h, which involves the fine-structure constant a,
the mass of the electron me, the speed of light in vacuum c,
and the Planck constant h, all of which we take to be
expressed in SI units. >>
http://www.aip.org/pt/vol-54/iss-3/p29.html


<< The quantity eps_0 defined in the MKS system of units as ()
where c is the speed of light, u_0 is the permeability of free space.
The unit F is a Farad, C is a Coulomb, and N is a Newton. >>
© 1996-2006 Eric W. Weisstein
http://scienceworld.wolfram.com/physics/PermittivityofFreeSpace.html

http://physics.nist.gov/cuu/Images/alphaeq.gif
http://physics.nist.gov/cuu/Constants/alpha.html
http://hyperphysics.phy-astr.gsu.edu/Hbase/waves/string.html

Sue...



PD




Sue...


.

Relevant Pages

  • Re: What is frequency??
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    (sci.physics.relativity)
  • Re: What is frequency??
    ... a transverse wave propagated along a medium like a string, ... of the medium and the inertia of the medium. ...
    (sci.physics.relativity)
  • Re: What is frequency??
    ... a transverse wave propagated along a medium like a string, ... of the medium and the inertia of the medium. ...
    (sci.physics.relativity)
  • Re: What is frequency??
    ... a transverse wave propagated along a medium like a string, ... of the medium and the inertia of the medium. ... Coulomb force and electron mass nicely accounts ...
    (sci.physics.relativity)
  • Re: What is frequency??
    ... a transverse wave propagated along a medium like a string, ... of the medium and the inertia of the medium. ...
    (sci.physics.relativity)