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