On 9/10/2015 3:03 AM, AndyW wrote:
On 09/09/2015 18:51, gareth wrote:
"gareth" wrote in message
...

AIUI, the wave / particle duality of the photon means that it has a
beginning
and an end, from the particle model.

The point of the duality model is that it appears to exist as both, or
may exist as something that exhibits the behaviour of both.

Don't want to be pedantic, but I think it is more that any given
experiment can show one or the other, but *not* both at once. Although
someone pointed out in another discussion that some experiment showed
both. It was an interference type of display, but the patterns were
formed of individual dots from individual photons. But I expect there
is another way to explain the results.... but above my pay grade.


Therefore, the wave model must exhibit amplitude modulation to have
such a
beginning and end.

Why must it?
It could have FM modulation or none at all. It could just start and end
(technically with a rectangular envelope but that would effectively be
no AM at all)
You do you claim it *must* have AM?

There is no reason to discuss this with him. He won't get what you are
saying. I guess he is picturing the quanta as a pulse of a wave which
it *isn't*.

There is also little reason for me to point out the futility of
discussing this with Gareth. Every so often he starts a discussion and
the band starts playing. I don't know who is stupider, Gareth or the band.

Bear in mind that my physics degree leans more towards macro physics and
the physics of materials rather then sub atomics and quantum. I'm a
little rusty on this.

Quanta at radio frequencies will be hard to prove. But as someone
pointed out, RF is emitted by individual atoms in an MRI scan. So
clearly that would be a quantum effect and not a continuous wave. I
believe this is due to the RF energy absorbed by the atoms causing them
to flip spin. After a relaxation time (basically a delay) they revert
to the ground state and emit quanta of RF energy. That is what the
magnet is for, to create a field that makes one orientation of spin the
"ground" state at a lower energy. I expect the frequency of RF will
depend on the strength of the magnet, but I'm not sure of that. I used
to do NMR scans (nuclear magnetic resonance) in chemistry. That was 40
years ago, so I don't recall if the exact frequency depended on the
magnetic field or just the molecular environment. We could tell
something about molecular structure by the frequencies of the resonances
much like other spectroscopy.

They used to call the medical usage NMR, but they wanted to get rid of
the "nuclear" part so it became MRI. "Nuclear" scares people.

--

Rick