The energy of photon is given by the equation $E=hf$, where $h=$ Planck's constant, and f=frequency of radiation. Is f quantized, or can it assume any value?
If it can assume any value, then wouldn't this mean that the energy of photons is not quantized? If f can be any value from a continuous series, this would mean that for any number you imagine, there will always be another number that when multiplied by h gives you that first number. So $E$ could assume any value.
However, we know that $E$ is indeed quantized, so could someone please point out the flaw in my reasoning?
PS: I don't believe this question is a duplicate, since it addresses wether radiation frequencies are discrete in the context of an equation. The answers, therefore, aren't limited to "no, the EM spectrum is not quantized" but also explain that for a given frequency, the photons' energy is quantized. In other words, while the questions are similar, I believe that both the question and the answers have angles that are different enough to justify not being duplicates. For example, if the answers to this question had not addressed the photon energy, I would still be confused as to why so many textbooks say that energy is quantized. This isn't the kind of answer that the duplicates would require, however. Thank you for linking the other posts, though, as they could be useful for someone looking for a different answer.