2

We know that E = hv

  • E = photon energy
  • h = Planck constant
  • v = frequency

We also know that photon energy E can only come in discrete values (quanta).

Does the combination of these two assumptions then determine that frequency, v can only come in discrete values as well?

======

Note on research: There are Phys.SE questions that are similar to mine, but none seem satisfactory, in terms of explaining how the equation can only take on discrete values.

Community
  • 1
Cole Bittel
  • 131
  • Frequency (and hence energy) is discrete when photon results from transition between two discrete states (in atoms for example – Lewis Miller Nov 17 '16 at 16:21
  • If you think of frequency as a measure of the number of cycles per second that occur for a given phenomena then I would say that those cycles are counted which would imply that they are discrete. The cycles that is. So, does that satisfy your question. – K7PEH Nov 17 '16 at 16:22
  • There are however many cases when this is not the case. For example Bremstrahlung, or breaking radiation where frequency may vary continuously. – Lewis Miller Nov 17 '16 at 16:23
  • 1
    Possible duplicates: http://physics.stackexchange.com/q/73959/2451 and links therein. – Qmechanic Nov 17 '16 at 16:41
  • @Qmechanic – My question is very specific to the relationship between two assumptions (the equation, and discretized energy). The link you provided doesn't relate the two. – Cole Bittel Nov 17 '16 at 16:49
  • @ColeBittel The question seems the same. You have the correct relation for a photon's frequency and energy, but you are making an assumption about photon creation that is relevant in a specific scenario. – anon01 Nov 17 '16 at 18:25

1 Answers1

2

You say:

We also know that photon energy E can only come in discrete values (quanta).

but this is not true. It is generally true that the energy of a bound system takes discrete values, but the energy of a free system has a continuous range and can take any value. Since for such a system the energy is not discrete it follows that the frequency is not discrete either.

John Rennie
  • 355,118
  • Ah! Can we go further and say that frequency for bound systems is discrete? – Cole Bittel Nov 17 '16 at 16:40
  • @ColeBittel: Even for a bound system there is always some uncertainty in the energies of the bound states due to the uncertainty principle, so the photons emitted during transitions in the bound system do not have precisely defined discrete frequencies. – John Rennie Nov 17 '16 at 16:49