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  • $\begingroup$ What are the spectral widths of the photons emitted by the Sun? Are those mostly narrowband photons of mixed frequencies or broadband homogenous “white” photons? $\endgroup$
    – Prof. Legolasov
    Commented Jan 7, 2021 at 16:00
  • $\begingroup$ @Prof.Legolasov may this answershttps://en.wikipedia.org/wiki/Sunlight#Composition_and_power $\endgroup$
    – anna v
    Commented Jan 7, 2021 at 16:37
  • 3
    $\begingroup$ @Prof.Legolasov Unfortunately it is not possible to measure the spectral width of a single photon from the Sun, or from any other source. The spectral widths of the wavefunctions of a large number of identically produced photons from a source can be determined statistically. $\endgroup$
    – S. McGrew
    Commented Jan 7, 2021 at 16:55
  • $\begingroup$ @S.McGrew I find it hard to believe that a measurement is impossible in principle for sunlight. Even if it is impossible in practice, we should be able to predict this using astrophysics $\endgroup$
    – Prof. Legolasov
    Commented Jan 8, 2021 at 0:55
  • 1
    $\begingroup$ I daresay “any photon has a finite spectral width” is, if not just wrong, then at least more confusing than helpful. Photons don't contain the information of how they were created in any meaningful (measurable) sense. They're just excitations of the EM field. Spectral uncertainty comes from certain properties of the whole system under consideration, not from anything about the individual photons. $\endgroup$
    – leftaroundabout
    Commented Jan 8, 2021 at 11:49