Re: Is photon a wave packet ?

[William Beaty <billb@ESKIMO.COM>]

On Thu, 16 May 2002, Larry Woolf wrote:

> The best answer is to get Feynman's QED and read chapter 2, Photons:
> Particles of Light.
>
> "people still tried to understand them in terms of old fashioned ideas (such
> as, light goes in straight lines).  But at a certain point the old fashioned
> ideas would be begin to fail, so a warning was developed that said, in
> effect, "Your old fashioned ideas are no damn good when ..." If you get rid
> of all the old fashioned ideas and instead use the ideas that I'm explaining
> in these lectures - adding arrows for all the ways an event can happen..."


Do you, personally, visualize physics exclusively in QED terms?  Or do you
still use concepts like "electric field" and "magnetic field?"

If you still use fields, I'd say that you demonstrate the error in
Feynman's assertion.  His method is too complicated a model to apply in
all situations.  His "old fashioned ideas" have another name: SIMPLIFIED
MENTAL MODEL.  To use any simplified model we must have clear knowledge of
its limitations, i.e. know exactly if it's "no damn good when..."
Analogy: fingernail clippers are far more precise than a lawn mower, but
just try mowing a lawn using fingernail clippers.  Or, just try performing
any simple curring task if you don't know the difference between the two.


While on the fly in a vacuum, light and radio waves are conceptually the
same.  The big difference arises during interactions (with metal coils
versus single atoms,) and when the radio waves are so weak that individual
quanta become important.


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