Richard Clark wrote:

On Tue, 09 Aug 2005 17:11:41 -0700, Jim Kelley
wrote:

There is no such thing in reality as a wave that delivers no energy.

See Born and Wolf for examples.


Hi Jim,

This is intriguing for a wave (I presume you were adhering to the
singular). For those who lack these references, do you have any
concrete examples?

73's
Richard Clark, KB7QHC

Hi Richard,

You may recall this came up before. The example I noted was in the
instance of total internal reflection. Page 47, "Principles of Optics"
Born and Wolf. When the angle of incidence with respect to the normal
exceeds the critical angle "no light enters the second medium. All the
incident light is reflected back into the first medium and we speak of
total reflection. Nevertheless the electromagnetic field in the second
medium does not disappear, only there is no longer a flow of energy
across the boundary." They footnote that an elegant experimental
demonstration is described by W. Culshaw and D. S. Jones Proc. Phys.
Soc. B 1954.

It's also arguable whether any energy is transferred from a source to a
lossless, open circuited, 1/2 wave transmission line after the transient
period. Though there's no uncertainty about the presence of
electromagnetic waves on such a line in the steady state.

73, Jim AC6XG

Jim Kelley wrote:
It's also arguable whether any energy is transferred from a source to a
lossless, open circuited, 1/2 wave transmission line after the transient
period.

Use a signal generator with a circulator load as the source. Cause a
noise glitch on the source signal. When will you see the glitch
across the circulator resistor? One cycle later. Reckon where that
glitch went during that one cycle? Man, that's a tough question. :-)
--
73, Cecil http://www.qsl.net/w5dxp


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Cecil Moore wrote:
Jim Kelley wrote:

It's also arguable whether any energy is transferred from a source to
a lossless, open circuited, 1/2 wave transmission line after the
transient period.


Use a signal generator with a circulator load as the source. Cause a
noise glitch on the source signal. When will you see the glitch
across the circulator resistor? One cycle later. Reckon where that
glitch went during that one cycle? Man, that's a tough question. :-)

I notice you opted to use the word 'glitch' rather than 'transient'. :-)

ac6xg

Jim Kelley wrote:

Cecil Moore wrote:
Use a signal generator with a circulator load as the source. Cause a
noise glitch on the source signal. When will you see the glitch
across the circulator resistor? One cycle later. Reckon where that
glitch went during that one cycle? Man, that's a tough question. :-)

I notice you opted to use the word 'glitch' rather than 'transient'. :-)

Yep, in order to avoid your inevitable copout: "But that's
not steady-state." There are natural noise glitches existing
in every real-world steady-state system. Those natural noise
glitches can be used to track the flow of energy in the EM
waves.

In the real-world, a system never achieves true steady-state
conditions because those natural noise glitches are always
present and, unfortunately for your argument, can be easily
tracked.
--
73, Cecil http://www.qsl.net/w5dxp

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On Tue, 09 Aug 2005 19:36:51 -0700, Jim Kelley
wrote:

There is no such thing in reality as a wave that delivers no energy.
You may recall this came up before. The example I noted was in the
instance of total internal reflection. Page 47, "Principles of Optics"
Born and Wolf. When the angle of incidence with respect to the normal
exceeds the critical angle "no light enters the second medium.

Hi Jim,

OK, and in relation to:

It's also arguable whether any energy is transferred from a source to a
lossless, open circuited, 1/2 wave transmission line after the transient
period.

But:

Though there's no uncertainty about the presence of
electromagnetic waves on such a line in the steady state.

is becoming strained language where so many struggle with English. Is
this to imply there's uncertainty about the presence of light that is
captured by total internal reflection? At the last census of total
cancellation, if it didn't meet a certain percentage it became
invisible. Something like an undocumented worker....

73's
Richard Clark, KB7QHC