# How do antennas generate photons?

I understand that in order to most quickly understand all aspects of electromagnetic radiation, the photon representation should be used in some cases and the macroscopic electromagnetic wave representation should be used in others. To preface my question, I want to say that I am pretty well educated in physics and have a bachelor's degree in the subject, so this is purely curiosity driven.

All of that being said, I am curious how a simple dipole antenna generates EM radiation on the level of photons. Again, let me emphasize, I realize this is not the optimal way to understand dipole antennas, I am just curious.

Say you have an AC voltage source connected to your dipole antenna. As the first part of the AC signal starts accelerating the electrons in one direction, I assume photons are being generated already? Considering this is a constantly changing acceleration (the signal is a sine wave, so is the acceleration of the charge), it seems the photons will have many different frequencies. And the exact same scenario stands for the acceleration of electrons in the other direction of the antenna. So are the EM waves that are generated in this fashion, with a macroscopic antenna being fed an AC voltage signal, really just a wide variety of photon frequencies that are mimicking the AC signal's frequency only by landing in the corresponding succession at the receiving antenna?

• Have a look at my answer here physics.stackexchange.com/questions/353602/… . At the electrons in the fermi level , the forced oscillation gives the correct frequency (e=hnu) to the dp/dt transfered to the electrons, and the timing the synchronous addition of the photon wave functions to build the dipole wave. Aug 28, 2017 at 6:31
• Aug 28, 2017 at 18:50

it seems the photons will have many different frequencies. And the exact same scenario stands for the acceleration of electrons in the other direction of the antenna.

That is exactly how an antenna works. The antenna generator is needed:

1. to accelerate the electrons forth and back the rod to generate photons and
2. to produce a carrier wave at the frequency to which the receiver is adapted.

The information is imprinted for example by frequency modulation or amplitude modulation.

So are the EM waves that are generated in this fashion, with a macroscopic antenna being fed an AC voltage signal, really just a wide variety of photon frequencies that are mimicking the AC signal's frequency only by landing in the corresponding succession at the receiving antenna?

That is exactly how the receiver works. A tiny amount of photons (in relation to the emitted amount of photons) hit the receiver, but again with the frequency of the wave carrier. And a lot of other EM radiation hits the rod too.

A filter has to let through the electrons, accelerated from the photons of the wave carrier frequency and after extract the information from the frequency or amplitude modulation.

Understanding this one has to clearly recognize the methodical difference between EM radiation (from IR/microwaves, visible light, UV, X- to gamma rays) and radio waves. The first in the most cases are thermal radiations, the last are modulated waves with photons from IR to X-rays. Dependent from the power the antenna could get warm or hot and it could dangerous to be near a broadcast antenna.