Frequency of photon and frequency of EM wave

Question

If I have a source of photons where photons have $f$ frequency and the emitting frequency of the source is $f'$, what is the frequency of the resulting EM wave?

Essentially, we have a source that emits photons that each have a frequency of f, but the frequency of their production by the source is f′.

What do you mean by the emitting frequency of the source? If the source is emitting light with a frequency $f$ then I don't understand what $f'$ is. Do you mean the source is modulating the light intensity at a frequency $f'$? — John Rennie, Jan 19 '17 at 13:02
I mean every single photon is emitted after another with f' frequency. But the own frequency of the photon is f. Think like a gun that shots with f' frequency the bullets — asv, Jan 19 '17 at 13:03
A light wave isn't made up of photons as if it was a stream of little balls of light, and it doesn't make sense to talk about a source emitting one photon every $1/f'$ seconds. The average power can correspond to $h\nu$ every $1/f$ seconds but that isn't the same as emitting a photon every $1/f$ seconds. — John Rennie, Jan 19 '17 at 13:06
See What is the relation between electromagnetic wave and photon? for more on this. — John Rennie, Jan 19 '17 at 13:07
" Light is not a wave nor a particle but instead it is an excitation in a quantum field. "
The QFT says what is this field phisically (apart mathematical objects)? There are theories that see this field like it was an excitation of spacetime? — asv, Jan 19 '17 at 13:33

score 2 · Accepted Answer · answered Jan 19 '17 at 13:52

2

If I understand you correctly, you're saying that you have a source that emits photons that each have a frequency of $f$, but the frequency of their production by the source is $f'$.

Well, then the frequency of the emitted waves is the same as the frequency of the photons, i.e. $f$. The rate of their emission doesn't matter.

answered Jan 19 '17 at 13:52

J. Pipiskin

264

This answer is basically correct but of course there is no such source that actually emits photons with a specific frequency of production. – Marty Green Jan 19 '17 at 14:22

Frequency of photon and frequency of EM wave

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