On 7 jul, 16:55, "Szczepan Bialek" wrote:
*"lu6etj" ...

D: Kraus says: "a charge moving at uniform velocity

along a curved or bent wire it is accelerated and radiates".
The clue was in words "straight wire" , he says: "Electric charge
moving with uniform velocity along a straight wire does not radiate".

This principle is used today to produce the light in the free electron
laser:http://en.wikipedia.org/wiki/File:FEL_principle.png
S*

Yes, very interesting example (and device),

Cecil it is right respect a photon/noise power ratio, even one photon
of 80 m per second it is very below of noise at 1 K, 80 m-quantum/
Noise dB ratio @1 Hz BW = -38 dB.

Respect to DC current EM radiation, In that time Richard bring an
interesting example of 20 kV electron rectilinear beam rendering a
frequency of 34.6 EHz, the calculus it was quite right, but that
frequency it is not EM waves radiated by electrons but a "matter wave'
frequency... (idem with car analogy = not charged and acelerated
cars :) do not radiates EM waves, but may have a matter wave
asociated to them).
For these reasons IMHO I think -as Cecil do-: basic (undergraduated?)
physics books are very useful to helping us to better understand and
enjoy our ham topics.

73 - Miguel