How does antenna tuning select the frequency of emitted photons?

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kishushah
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If electric energy is supplied in the form of high voltage & low current & if the same energy is supplied in the form low voltage & high current will there be in difference in the photons emitted by the antenna?the frequency is same for both the cases.One electron can interact with just one atom & bring it to the excited state?and what is antenna tuning?why by doing so you can get the photons of that tuned frequency? & why the electric wave of the same frequency is required to be fed to the antenna?Give detailed explanation of all these queries.
 
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hey nobody is here who can explain me these things?
 
First comment: an antenna doesn't perform like a transformer which you can use to switch from high voltage-low current to low voltage-high current. Since an antenna has a frequency dependent impedance, radiating a desired amount of power calls for a specific voltage.
Beyond this fact, if the frequency stays de same, every photon carries the same amount of energy. A high power transmitter sends more photons per unit time
 
As the radio wave reaches the antenna and the peak voltage amplitude reaches the ends of a dipole antenna, the electric field reaches a maximum and the current along the antenna and thus the magnetic field around the antenna go to minimum.

Then as the voltage reverses, the voltage at the ends of the antenna decreases to zero and the current along the antenna increases to maximum. So you get high voltage and low current AND low voltage and high current twice every cycle. Both are needed to produce photons.

One electron can interact with just one atom & bring it to the excited state?
Did you mean "photon" instead of "electron"?

Don't forget that the electric and magnetic fields of an antenna that oscillate at the frequency of the applied signal are also composed of photons.

You can drive an antenna with a signal that is not resonant with the antenna but that makes the antenna much less efficient so we try to avoid doing that.
 
I don't want to perform transformer action.my question here is completely different.Just go through it once more may be things will be little bit more clear to you.


You are talking about antenna and radiation things at classical level i want the explanations at the atomic level.In antenna energy carried by the electrons is transferred to the atoms and they are brought to excited state and when they come back to normal state they emit photons.
 
kishushah said:
In antenna energy carried by the electrons is transferred to the atoms and they are brought to excited state and when they come back to normal state they emit photons.

No. Have you seen antennae glowing with the characteristics wavelengths of the atoms from which it is made of?
 
You can't see them they are not in the visible range.they are having frequency in terms of MHz to GHz.
 
kishushah said:
I don't want to perform transformer action.my question here is completely different.Just go through it once more may be things will be little bit more clear to you.


You are talking about antenna and radiation things at classical level i want the explanations at the atomic level.In antenna energy carried by the electrons is transferred to the atoms and they are brought to excited state and when they come back to normal state they emit photons.

Antennas do not radiate by exciting atoms. If that was the case then the physical structure of the antenna would not determine its operating frequency but rather its material make up. Antennas radiate by acting as a "transformer" to mediate a guided electromagnetic wave into a propagating electromagnetic wave. The wave already exists, it is guided along the transmission lines in the antenna's feed to the antenna. The antenna then directs the energy of the wave out into open space where some of the energy becomes a propagating wave. Another way to think about it is that the induced voltages on the antenna's feed cause the charges to accelerate in the antenna. Accelerating charges radiate electromagnetic waves. While this may be a more conceptually easier to understand explanation I do not think it the better one because these charges are more accurately being induced to move by the electromagnetic waves themselves. I think it can imply a reversal of the causality of the situation.
 
They are tuned for a specific frequency so the structure plays the role here not not the material make up.

And yeah the concept of transformer is used only but not for the task the transformer we usually employ that's what i was trying to say.

You are not exactly explaining how waves are radiated.there should be some reason for that why the energy in the transmitting line is propagating in the open sky.how you can apply the concept of photons here?I need some explanation at atomic level what actually happens there?

By what action antenna is emitting photons?Please explain this thing to me.Not by wave theory but by particle theory.
 
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how energy carried by electrons is converted into energy in form of photons by antenna?
 
There isn't anything happening on the atomic level that isn't already adequately described by the classical theory. You excite an electromagnetic wave at your source and you do so inside of a waveguide. The waveguide is structured in a way that directs the propagation of the wave along a desired direction. This waveguide feeds into the antenna. The antenna acts as a transition from guided to propagating wave and vice-versa. A lot of times this can be seen as a direct physical process as we describe. For example, we can feed the wave into a resonant chamber that allows radiation to leak out in a desired direction. This can be done by leaving gaps in the chamber. This is roughly how a patch antenna works. The area between the patch and the ground acts as a resonant chamber to trap the energy of the guided wave. But the sides of the chamber are open and thus energy can leak out of the sides (or in in the case of receiving).

A horn antenna works by gradually transitioning a rectangular waveguide into an infinitely open waveguide (ie, free-space). This is done by steadily increasing the size of the waveguide and thus you get a horn. Ideally it would keep increasing to an infinite size but in the interests of reality we have to truncate the horn at some point.

A dipole antenna is a rough realization of a horn antenna. The wave is guided between the two arms of the antenna and then the wires suddenly separate allowing for the guided wave to hit the gap and propagate out. Think of the arcing in a Jacob's Ladder.

The energy isn't carried by the electrons. It is carried by the electromagnetic wave and it is the wave that excites these currents. However, electromagnetic waves and currents are for the most part inseparable. When you have one you have to have the other and thus the lines of causality can be a bit blurred. Take the case of sourcing the electromagnetic waves. Do you do this by exciting an alternating electric field which creates an electromagnetic wave that then induces the currents in the waveguide? Or do you excite the currents in the waveguide which create the electromagnetic wave? I do not think that this is really that ambiguous. Technically we do not really have many (if even) means of exciting currents without first inducing an electric field to direct the currents in the manner that we wish. Still, it can become confusing sometimes. In the case of antennas and waveguides, the actual source currents are back at the generator of the electromagnetic wave. All the other currents along the waveguide and on the antenna and so forth are induced by the resulting electromagnetic waves since the source currents and voltages are localized.

Now in terms of photons, the photon is simply the carrier of the energy of the electromagnetic wave. So the amplitude and direction of propagation of the wave is indicative of the density and direction of movement of the photons that make up the wave.
 
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