Re: "A Snapshot of a Photon"

John Kennaugh wrote:
Physics cannot keep switching between a wave and a particle whenever it suits.

We don't. These are QUANTUM OBJECTS, and are _NEITHER_ wave nor particle. If you want to think of them as such, you need to realize that nature has no need to do things in a way you feel comfortable discussing in terms familiar to YOU. Quantum mechanics is considerably more subtle than you think....


Somehow the two descriptions must be reconciled.

No. You need to learn how to discuss QUANTUM OBJECTS rather than "waves" or "particles".


> [... bunch of confusion based on the above error]

Tom Roberts wrote:
Physicists know that the frequency of a photon is uncertain....

How can it be? If the energy of a photon = hf. The uncertainty of the frequency is related to the uncertainty of the energy. 

The frequency is also uncertain.


"Question: Why are the wavelengths of the spectrum lines from a gas in a discharge tube so precisely defined? .
Answer: Because the permitted energies that electrons can assume within the atoms are precisely quantized.

They may be quite precise, but they are not exact -- there remains some uncertainty in the energy levels, and consequently in the energy and frequency of the emitted photon. Heisenberg's uncertainty principle implies that the linewidth of a transition from atomic state A to state B is related to their lifetimes -- longer lifetimes implies narrower linewidth; a "perfectly narrow" linewidth requires an "infinitely long" lifetime, and it will never emit any photons.

	[This is an oversimplification....]


Question: Oh - I thought it was the electron's angular momentum that was quantized?
Answer: That is also true. Both energy and angular momentum are precisely quantized.

Not precisely -- there remains some uncertainty. But for some situations the uncertainty can be smaller than the resolution of the measurement device (which consequently dominates).


I am not saying it is possible to generate by any known means, but I see no reason in theory why a burst of photons, all with the same energy could not exist in nature.

Not _exactly_ the same energy, only _approximately_ the same energy, subject to the limits implied by the Heisenberg uncertainty principle.


Get a book on quantum mechanics. STUDY it. Attempting to do physics by blind guesses is hopeless. As is attempting to do physics by sound bite ("particle vs wave").


Tom Roberts	tjroberts@xxxxxxxxxx
.

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