How does a radio antenna work quantum mechanically?
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From: Benj on 29 Jul 2010 23:13 On Jul 29, 7:54 pm, Darwin123 <drosen0...(a)yahoo.com> wrote: > On Jul 29, 7:12 pm, "Androcles" <Headmas...(a)Hogwarts.physics_z> wrote: > You have often claimed to be an engineer. What type of engineer > were you? > You clearly don't know classical physics. . How > much electrical engineering do you know? You are asking Andro how much he knows? Surely you jest!
From: Darwin123 on 30 Jul 2010 00:44 On Jul 29, 5:42 pm, Excognito <stuartbr...(a)gmail.com> wrote: > Is there a good reference that explains these kind of issues from a > "what's going on in this situation" perspective? I don't know if Wikipedia can be called a "good" reference, but it does discuss these types of issues. Here are two Wikipedia articles. http://askbluey.com/wikipedia/View.aspx/Near%20and%20far%20field?q= Ask Bluey on Wikepedia In the quantum view of electromagnetic interactions, far field effects are manifestations of real photons, while near field effects are due to a mixture of real and virtual photons. Virtual photons composing near-field fluctuations and signals, have effects which are far shorter range than do real photons. http://en.wikipedia.org/wiki/Virtual_particle Virtual particle Virtual photons are also a major component of antenna near field phenomena and induction fields, which have only very short-range effects, that do not radiate through space with the same range- properties as do electromagnetic wave photons. For example, the energy carried from one winding of a transformer to another, in quantum terms is carried by virtual photons, not real photons. The so-called near field of radio antennas, where the magnetic and electric effects of the changing current in the antenna wire and the charge effects of the wire's capacitive charge are detectable, but both of which effects decay with increasing distance from the antenna much more quickly than do the influence of conventional electromagnetic waves, for which E is always equal to cB, and which are composed of real photons.
From: Uncle Ben on 30 Jul 2010 07:39 On Jul 30, 12:44 am, Darwin123 <drosen0...(a)yahoo.com> wrote: > On Jul 29, 5:42 pm, Excognito <stuartbr...(a)gmail.com> wrote: > > > Is there a good reference that explains these kind of issues from a > > "what's going on in this situation" perspective? > > I don't know if Wikipedia can be called a "good" reference, but it > does discuss these types of issues. Here are two Wikipedia articles. > > http://askbluey.com/wikipedia/View.aspx/Near%20and%20far%20field?q= > Ask Bluey on Wikepedia > In the quantum view of electromagnetic interactions, far field > effects are manifestations of real photons, while near field effects > are due to a mixture of real and virtual photons. Virtual photons > composing near-field fluctuations and signals, have effects which are > far shorter range than do real photons. > > http://en.wikipedia.org/wiki/Virtual_particle > Virtual particle > Virtual photons are also a major component of antenna near field > phenomena and induction fields, which have only very short-range > effects, that do not radiate through space with the same range- > properties as do electromagnetic wave photons. For example, the energy > carried from one winding of a transformer to another, in quantum terms > is carried by virtual photons, not real photons. > The so-called near field of radio antennas, where the magnetic and > electric effects of the changing current in the antenna wire and the > charge effects of the wire's capacitive charge are detectable, but > both of which effects decay with increasing distance from the antenna > much more quickly than do the influence of conventional > electromagnetic waves, for which E is always equal to cB, and which > are composed of real photons. Thank you for this discussion. I am a ham radio operator and a physicist, but not a master of QED. You have helped me understand these matters. Don't mind Androcles. He has argued that there is a smallest real number greater than zero, and that Einstein mistakenly derived that moving rods expand, not contract. Uncle Ben
From: Androcles on 30 Jul 2010 08:05 "Uncle Ben" <ben(a)greenba.com> wrote in message news:159aba69-16ba-40b5-9015-cf223568c494(a)l14g2000yql.googlegroups.com... On Jul 30, 12:44 am, Darwin123 <drosen0...(a)yahoo.com> wrote: > On Jul 29, 5:42 pm, Excognito <stuartbr...(a)gmail.com> wrote: > > > Is there a good reference that explains these kind of issues from a > > "what's going on in this situation" perspective? > > I don't know if Wikipedia can be called a "good" reference, but it > does discuss these types of issues. Here are two Wikipedia articles. > > http://askbluey.com/wikipedia/View.aspx/Near%20and%20far%20field?q= > Ask Bluey on Wikepedia > �In the quantum view of electromagnetic interactions, far field > effects are manifestations of real photons, while near field effects > are due to a mixture of real and virtual photons. Virtual photons > composing near-field fluctuations and signals, have effects which are > far shorter range than do real photons.� > > http://en.wikipedia.org/wiki/Virtual_particle > Virtual particle > �Virtual photons are also a major component of antenna near field > phenomena and induction fields, which have only very short-range > effects, that do not radiate through space with the same range- > properties as do electromagnetic wave photons. For example, the energy > carried from one winding of a transformer to another, in quantum terms > is carried by virtual photons, not real photons.� > �The so-called near field of radio antennas, where the magnetic and > electric effects of the changing current in the antenna wire and the > charge effects of the wire's capacitive charge are detectable, but > both of which effects decay with increasing distance from the antenna > much more quickly than do the influence of conventional > electromagnetic waves, for which E is always equal to cB, and which > are composed of real photons.� Thank you for this discussion. I am a ham radio operator and a physicist, but not a master of QED. You have helped me understand these matters. Don't mind Androcles. He has argued that there is a smallest real number greater than zero, and that Einstein mistakenly derived that moving rods expand, not contract. Uncle Ben ================================================= You have your adverbs mixed up. You are a radio operator and a ham physicist. Androcles DEFINED the smallest real number greater than zero to be h, and Einstein derived that moving rods expand, not contract. Whether it was a mistake or not is a different matter. Don't mind Napoleon Bonehead, he's an incompetent idiot. Virtual photons in transformers... bwahahahahahahahaha!
From: nuny on 30 Jul 2010 08:26
On Jul 29, 2:42 pm, Excognito <stuartbr...(a)gmail.com> wrote: > What are the physical processes, from a quantum perspective, involved > in receiving/transmitting radio waves? Bits (quanta) of stuff have quantized charges and can only gain and lose energy in lumps (quanta). They do that by exchanging real (quantized) and virtual (unquantized) photons, as you've been told. After that it gets a little complicated. > Eg, if an electron undergoes acceleration in a magnetic field, is the > magnetic force mediated by photons? Yes. What else? > When the accelerating electron > radiates, does it do so by emitting radio energy quanta? How else? Not necessarily "radio" though; rather "EM radiation". Covers the whole spectrum that way. > If so, does > that mean that the electron's trajectory is a sequence of linear steps > rather than a continuous curve? Yes. Irrelevantly tiny steps to most radio antennae. Also, they don't have infinitely sharp corners. > Assume a conducting wire antenna lying normal to the direction of > propagation of a radio 'wave' (what is the structure of this 'wave' in > terms of a photon model?). Interlocking E and M fields traveling together. You want pictures and diagrams? They're all over the internet. The wave is whatever the hell it "really" is. What we can measure, we have names for. As measuring ability gets better we find names for the stuff we can see. Whether or not we get "all the way down" at some point will annoy phiiosophers and scientists forever, if for different reasons. > When a radio photon interacts with an > electron in a conductor, how does the (linear?) momentum of the photon > get converted into electron motion in a specific direction along the > antenna? The linear momentum of the photon is alternately "invested" as transverse E and M fields, yes. If the photon's E field manifests near an electron, it "pushes" the electron *this* way, while the photon refracts a bit *that* way. Momentum is conserved. > Is there a good reference that explains these kind of issues from a > "what's going on in this situation" perspective? "What's going on" in what terms? Mark L. Fergerson |