# If an electromagnetic wave is very very weak, e.g., its energy flux density is less than $h\nu/(\mathrm{m^2\cdot s})$, is there any photon please?

A simple but not very simple question please!

If an electromagnetic wave is very very weak, e.g., its energy flux density is less than $h\nu/(\mathrm{m^2\cdot s})$, can there be any photon appearing and can it be detected? $\nu$ is the frequency of the EM wave.

If we consider the EMW is consist of photons, there will be no EMW at all because its energy is even less than a single photon. Am I correct please?

• Note that you may have one photon every hour, for example. Then the flux will be quite small indeed. – Blazej Dec 23 '17 at 15:38
• Why do you think 1 square meter times one second would be anything special? – Norbert Schuch Dec 23 '17 at 16:25
• thank you for comment,..... im not thinking it special, just an example.....:) – justaskphysics Dec 24 '17 at 16:14

Yes, if you try to detect this radiation, you will only detect it in quanta of $h\nu$. But a detector with area 1 m2 will detect (on average) fewer than one photon per second. For example it might detect 1 photon (on average) every 2 seconds, or one photon every hour.