Re: Gaussian statics law

John Smith I wrote:
Cecil Moore wrote:
John Smith I wrote:
Really? I am going to have to see that one to believe it (not saying it is incorrect though), a "something" with no mass--kinda like a "ghost particle!"
It's old hat knowledge, John, and one of the reasons
why standing wave energy doesn't just stand there or
just "slosh around" as one guru asserted. If a photon
is slowed to zero velocity, its mass vanishes and
...

Cecil:

One more thing ... On those those frisky, frolicking photons.

What would you attribute the fact the "photons" in HF behave much differently then then the photons of VHF/UHF/SHF/LIGHT to?

That isn't quite true. The big gap is between anything we'd normally call "light", and anything we'd normally call "RF".

Long explanation coming up... Executive Summary: at normal radio frequencies, quantum theory is totally irrelevant.

Quantum theory describes electromagnetic energy as being divided into a series of packets called photons, so (total energy in a stream of photons) = (number of photons/second) x (energy of individual photons).

This also means that EM energy doesn't exist in pure sine-waves - the waveform is actually built up in steps, very much like digitized audio. The step size is the energy content of one quantum.

The question is: are those steps noticeable enough to be important?

For light and shorter wavelengths, the answer is often Yes. Quantum theory was developed to explain observations like some kinds of light being emitted in a series of sharp spectral lines, which cannot be explained by a wave-only theory. Instead, it has to be thought of as being built up of individual photons/quanta which can only have certain "allowed" energy levels.

It turned out that the energy content of a single photon is uniquely related to the wavelength of the radiation. Any given wavelength has only one quantum energy. More energy can only be made up from larger numbers of the same identical quanta. That unique quantum energy is inversely proportional to the wavelength, and directly proportional to the frequency:

E = hf

where
E is the energy content of a single quantum/photon (joules),
f is in Hz
h is Planck's constant which has a value of 6.6 x 10^-34 joule seconds.

This applies to all forms of EM energy, so let's calculate the 'step size' in an RF waveform at 10MHz. That will be the energy content of a single quantum, which turns out to be 0.000 000 000 000 000 000 000 000 0066 joules - which is unimaginably small.

It means that an RF waveform must be quantized into unimaginably large numbers of tiny steps. Those steps will NEVER be observable, and there will NEVER be any noticeable quantum effects at RF.

That holds true for all frequencies up to at least 100 gigahertz (millimetre wavelengths), where quantum effects just begin to be noticeable in precision measurements of very low noise levels - but even way up there, quantum effects are still only a small correction.

So after all that, we come back to the plain fact that normal RF radiation behaves purely as waves, just like we always thought it did. The only new information from quantum theory is to *confirm* that classical EM theory is all you'll ever need.




--

73 from Ian GM3SEK 'In Practice' columnist for RadCom (RSGB)
http://www.ifwtech.co.uk/g3sek
.

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