Użytkownik "Szczepan Bialek" napisał w wiadomości
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"K1TTT" wrote
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On May 9, 10:30 am, "Szczepan Bialek" wrote:
"tom"
se.net...
On 5/8/2010 2:04 PM, Szczepan Bialek wrote:
Yes. But one end of the dipole may have the better conditions to
propagate.
if it only moves in one direction as it would have
to in a monopole there is no wave only a simple field.
I am writing about a dipole with one end visible and the second
shielded.
In nature is always as you wrote. The both ands are always "visible".
Light is always directional. Radio waves can be omnidirectional.
Of course light is emitted by many dipoles. Radio waves by halve, one,
two
(circular polarity) or many (phase radar).
S*
Astonishing understanding of the subject.
Light is not coherent. So dipole radiate for very short time.
Radio waves are coherent and can be from one source. It is easy to
analyse
them.
Are they transversal?
S*
light can be coherent, what do you think lasers are?
"The most monochromatic sources are usually lasers; such high
monochromaticity implies long coherence lengths (up to hundreds of
meters). For example, a stabilized helium-neon laser can produce light
with coherence lengths in excess of 5 m. Not all lasers are monochromatic,
however (e.g. for a mode-locked Ti-sapphire laser, ?? ? 2 nm - 70 nm).
LEDs are characterized by ?? ? 50 nm, and tungsten filament lights exhibit
?? ? 600 nm, so these sources have shorter coherence times than the most
monochromatic lasers". From:
http://en.wikipedia.org/wiki/Coherence_(physics)
Up to now light is not coherent. But in future who knows.
"As the electrons are undergoing acceleration they radiate electromagnetic
energy in their flight direction, and as they interact with the light
already emitted, photons along its line are emitted in phase, resulting in a
"laser-like" monocromatic and coherent beam. The mirrors show in the sketch
below are superfluous, as all the light is emitted in one direction anyway."
From:
http://en.wikipedia.org/wiki/Halbach_array
So we have the light like the radio waves: Monocromatic and coherent. But it
is not from plain lasers.
S*