Chronology Current Month Current Thread Current Date
[Year List] [Month List (current year)] [Date Index] [Thread Index] [Thread Prev] [Thread Next] [Date Prev] [Date Next]

Re: [Phys-L] Photons and radio waves



One more thing: While we are talking about photons, beware that
the word "photon" is routinely used with two different, inconsistent
meanings.

In the context of an electrical harmonic oscillator, such as one
standing-wave mode of the electromagnetic field, we say that the Nth
energy eigenstate has N “photons” in it. The operator a†a is the
photon-number operator. These photons do not propagate at the
speed of light; indeed they do not propagate at all.

In the context of a propagating wave, a “photon” is a wavepacket,
typically a Gaussian wavepacket, with some not-too-large spread
in position and also some not-too-large spread in momentum.

Add this to the list of technical terms that are just different
enough /and just similar enough/ to get you into trouble.
energy
conservation (conservative flow, conserve wildlife, conservative force)
acceleration
photon
charge (charge on terminal versus gorge on capacitor)
spin
adiabatic
heat (four or five different meanings)
.... et cetera ....

=======================================
Also:

On 10/06/2013 09:51 AM, rjensen@ualberta.ca wrote:
From a very simplistic perspective, radio waves behave like waves --
they have sufficient wavelength to propagate around large objects. On
the other hand, once you get into the microwave and higher frequency
regions, the waves behave more like particles and reflecting off of
objects.

That's true as stated, but I don't think it answers the question
that was asked.

Reflection versus diffraction depends on the wavelength relative
to the size of the obstacle. Waves -- even with verrry long
wavelengths -- will exhibit specular reflection if they hit
something big enough. Hint: seismology. This is entirely
classical, with no hbar involved.

In contrast, the original question asked about quantization,
so I reckon the answer needs to involve hbar.