To the question regarding the relation between the energy of a photon (E = hf) and the energy of the associated electromagnetic wave, I read somewhere that the energy of an electromagnetic wave is Nhf, N representing the number of photons per second that pass through a unit area. How could the electromagnetic wave associated with a single photon produce several photons? If I read it wrong and it isn't, how can we represent the electomagnetic wave associated with a single photon and what would be its energy as a function of its frequency. Regards

  • $\begingroup$ I suspect part of your confusion is due to the wave-particle duality inherent in trying to describe a situation either in terms of (continuous function) waves or in a stream or cloud of particles. $\endgroup$ – Carl Witthoft Aug 4 '20 at 11:42
  • $\begingroup$ Thank you; I think so too. $\endgroup$ – Jean-Michel Tengang Aug 4 '20 at 14:09

The energy of a single photon is $E=hf$ which also corresponds to an electromagnetic wave of frequency $f$. If the beam of light consists of multiple photons, then the total energy of the beam of light equals the number of photons in the light beam $\times$ the energy of a single photon: $E_{tot}= Nhf$. In the wave framework, this can be seen as the superpostion of all the $N$ electromagnetic waves of frequency $f$. This resulting superposition is also a wave.

So, it can be that the total electromagnetic wave consists of the superposition of $N$ "fundamental" electromagnetic waves. Here, the $N$ "fundamental" electromagnetic waves correspond to the $N$ photons.


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