General > General Technical Chat
How does the electron make a photon in an antenna?
Sal Ammoniac:
Keep in mind that QED describes what happens, not how it happens. There's nothing in the theory, or any other theory, that describes how an electron converts excess energy into a photon, just that it does.
aetherist:
--- Quote from: karpouzi9 on January 31, 2023, 06:12:47 pm ---
--- Quote from: aetherist on January 31, 2023, 11:38:00 am ---
--- Quote from: calexanian on February 07, 2017, 05:47:16 am ---I was taught, and I just did some google searching because its been so long, is that the actual radio wave propagation (In the common communication ranges) is purely electromagnetic and electrostatic based on Maxwells equations. They propagate independent of photons in a manner dictated by QED. The photons are just an emitted byproduct generated by the intrinsic energy of the signal itself. In other words an antenna is producing the EM field, but any photons that are being released are not the principal emission and nowhere near the frequency of the base band, or in other words the antenna does not emit electrons or photons as a primary mode, only fields. It emits no more photons than any other piece of metal with that amount of energy going on about it. Things get a bit more complicated as you go higher up in frequency though. Via QED more "Loss" of energy is expressed via photons until you have an infrared light source. Somebody please correct me. Like I said. It has been a very long time.
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Wow - i just then read this -- i thort that this forum (& modern electricity & radio) was populated with idiots -- but calexanian is a breath of fresh air -- yes, radio waves are not photons -- radio waves are em radiation.
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:bullshit:
Radio waves are *made* of photons and those photons *do* have wavelengths that match the wavelength of the bulk RF emission. Bulk RF emission (radio waves) are packets of coherent photons. You can filter them down with attenuators until they're at the single-photon-per-second level, and those photons will mostly have wavelengths around the same wavelength as the bulk RF signal.
To elaborate on the negative: if you want to describe the output of a 2.4 GHz antenna connected to a 2.4 GHz oscillator, it is not "photons with a frequency of 1.3 GHz" or "photons with a frequency of 720 GHz" or something like that. It is photons with a frequency distribution centered around 2.4 GHz.
Otherwise, there would be no point engineering passive nanostructures with length scales around the relevant wavelength as single-photon emitters: https://pubs.acs.org/doi/10.1021/acsphotonics.7b00061
Just because you can knock a hammer (or short a charged capacitor) on a bell tuned for 200 Hz (or an antenna tuned for 1 MHz) and make it ring, for the briefest of moments, at 20 Hz (or 100 kHz) does not mean the bell's (antenna's) normal mode of operation is to emit acoustic waves (photons) of random frequencies. If you let the micro-scale (electron-scale) dynamics settle for a bit, the device will ring at whichever frequency it was tuned for.
--- Quote ---And, re the OP -- electricity aint due to the movement of electrons -- neither in the Cu nor on the Cu.
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A statement this vague yet absolutist qualifies as trolling. One could argue either side because the framing is nonsensical. Are you even talking about RF or just bulk electricity? Are you talking about the electron-scale dynamics that we refer to generally as "electricity," or are you talking about sparks and smoke and magic shows? Any way you pick, electrons are moving!
Unless you'd like to show us how to create radio emissions and/or "electricity" from nothing but crystalline structures (say, quartz) with "fixed" positive and negative charges without applying any heat, mechanical shock, acoustic waves, photons, or mechanical stress, and without waiting for their atoms to decay. Good luck :-+
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I accept your challenge. My answer will take me about 1 second of thinking, & a few minutes of typing. It goes like this.
In a crystal atom elektrons (photons) orbit (hug) the nucleus, ie elekticity orbits the nucleus, ie a shock etc can dislodge an elerton, & the elekton can then propagate along (hug) a conductor (eg a Cu wire), in which case we have elekticity.
What is vague about my saying that elekticity on a wire is due to elektons propagating along (hugging) the surface of the Cu?
What is vague about my saying that an atom is elekticity orbiting a nucleus?
Veritasium & others have said that electricity on a wire is not due to the movement of electrons -- & i agree (with that simple statement) – but then Veritasium & Co launch into some krapp about the Poynting Vector or Poynting Field being the carryer of the electrical energy (No).
So, u should firstly have a fight with Veritasium & Co -- & if u win that then come & see me (i have truth & facts in my corner).
But, back to the main topic re radio not being photons.
I reckon that radio is due to em radiation. U say that radio is due to photons.
Photons have a natural frequency. Em radiation duznt have a natural frequency – in radio it has a forced frequency.
Em radiation is emitted by every photon, ie it is emitted by elektons propagating upndown a transmitting antenna.
The em radiation emitted by elektons will mimic the elektons movement upndown theantenna.
A 1MHz antenna emits a 1 MHz em radiation wave, not a 1MHz photon.
In the receiver the em radiation will excite the elektons already on the Cu -- & will create a mini-version of the elekton current on the transmitter.
aetherist:
--- Quote from: karpouzi9 on January 31, 2023, 06:22:25 pm ---Uh-oh. Seems I've taken the opinion of someone who thinks electrons are photons seriously! Shame on me.
If I disagree with aetherist, he gets off on people reading and unavoidably amplifying his fantasy takes. If I ignore his posts, readers have to think and judge whether or not his claims are accurate for themselves, possibly without evidence, possibly spreading his fantasies to others. Never would have thought I'd run into Facebook-grade social dynamics on an engineering forum, but here we are. ::)
I'll just take this opportunity to plug Griffiths' QM instead: https://www.fisica.net/mecanica-quantica/Griffiths%20-%20Introduction%20to%20quantum%20mechanics.pdf
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Does Griffiths tell us what electricity is, & what radio is?
aetherist:
--- Quote from: TimFox on January 31, 2023, 06:59:24 pm ---The fundamental reason is that charge radiates when it is accelerated.
In an antenna, the oscillating current accelerates the conducting charge along the wire.
In a synchrotron, charged particles are accelerated centripetally (by appropriated magnetic fields) to follow an approximately circular orbit.
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NO. Charge duznt radiate when accelerated. Charge radiates all of the time. But, when a charge is at rest then the radiation is impotent. When charge is accelerated the radiation become potent, ie it can then have effect, ie it can then produce a force in some instances.
NO. In a transmitting antenna there is no conducting charge. In an antenna the oscillating elektons going upndown the Cu have their own charge, an elekton has a negative charge.
NO. Elektons going upndown an antenna do not ever accelerate. They always propagate at the speed of light. They have one speed. The signal going upndown an antenna will have a say sinusoidal form, & this sinusoidal form is due to the numbers of electons flying in formation, it aint due to any acceleration of the elektons.
In a synchrotron i suppose that electrons etc are made to follow a circular path at high speed (i say made, made to follow, by em radiation) – that sounds ok to me – here the electrons are electrons, they are not elektons, & they are not free photons (they are photons that have formed a loop by biting their own tail).
Sal Ammoniac:
--- Quote from: aetherist on January 31, 2023, 10:33:23 pm ---Charge radiates all of the time. But, when a charge is at rest then the radiation is impotent.
--- End quote ---
Please explain what you mean by "impotent" -- this isn't a very descriptive term when applied to charged particles emitting radiation.
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