Szczepan Białek wrote:
Heck, only a few years ago they said a
particle could exist without mass.
Photons have zero *rest* mass. If they had mass at
rest, they could not travel at the speed of light.
The mass of a photon is due to its velocity, c in
free space. When a photon slows to less than the speed
of light in a medium, it gives up its energy to another
particle, e.g. an electron, and disappears.
3. Photons
EM radiation from amateur radio antennas is photonic.
RF energy is supplied to the antenna system by our
transmitters. Free electrons are accelerated and
decelerated. Photons are emitted and absorbed by
those free electrons. Some of the photons escape
into space as coherent radiation.
One can learn a lot about EM waves by understanding
the nature of photons. For instance, standing waves
consist of photons that cannot stand still. The
illusion of a "standing" wave is just two waves of
photons moving in opposite directions at the speed
of light. Photons are not like mashed potatoes.
--
73, Cecil, IEEE, OOTC,
http://www.w5dxp.com