Science > Physics > Does a radio signal at the frequency of light generate light or an EM wave?
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Science > Physics |
| User: |
"" |
| Date: |
01 Apr 2005 11:36:05 AM |
| Object: |
Does a radio signal at the frequency of light generate light or an EM wave? |
I did not know that electromagnetic radio waves were a form of photon
(perhaps a photon vibrating at a different frequency?); I thought they
were electrons transmitted through the air or space.
I was wondering if one generates a radio signal at the frequency of
light, does it generate light or only a radio electromagnetic wave?
And are these waves, wether light or electromagnetic waves, harmfull to
the body or eyes (similar to gamma and x-rays)?
If it does generate light then is it multi-directional ondulatory light
waves (from the antenna's tip into a circular wave that propagates
wider and wider from the point of transmission) or is it a light beam
(such as a laser or a lightning/static single beam = mono-directional)?
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| User: "Bill Hobba" |
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| Title: Re: Does a radio signal at the frequency of light generate light or an EM wave? |
01 Apr 2005 02:43:00 PM |
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<guskz@hotmail.com> wrote in message
news:1112376965.781659.268090@z14g2000cwz.googlegroups.com...
I did not know that electromagnetic radio waves were a form of photon
(perhaps a photon vibrating at a different frequency?); I thought they
were electrons transmitted through the air or space.
That is very basic. Before posting again you might like to consider
becoming better acquainted with the basics of physics. I suggest the
Feynman Lectures on Physics
http://www.amazon.com/exec/obidos/tg/detail/-/0201021153/qid=1112387792/sr=8-3/ref=pd_csp_3/002-1917686-0881622?v=glance&s=books&n=507846
I was wondering if one generates a radio signal at the frequency of
light, does it generate light or only a radio electromagnetic wave?
A radio signal at the frequency of light is EM radiation at the frequency of
light so is light.
And are these waves, wether light or electromagnetic waves, harmfull to
the body or eyes (similar to gamma and x-rays)?
Since it is light then obviously it is just as harmful or not harmful as
light but see what I say below.
If it does generate light then is it multi-directional ondulatory light
waves (from the antenna's tip into a circular wave that propagates
wider and wider from the point of transmission) or is it a light beam
(such as a laser or a lightning/static single beam = mono-directional)?
See http://physics.ucsd.edu/~tmurphy/phys10/lectures/19_radio.PDF. Light is
usually randomly polarized meaning each photon has a random polarization.
It takes a special source such as lasers for it to have a specific
polarization like radio waves. Regarding your question above if 'radio wave
light' is more harmful than ordinary light I suppose in a certain sense it
is because lasers can be pretty dangerous as the beam is coherent
http://www.meos.com/Laser%20fundaments/laser_safety.htm
Bill
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| User: "T Wake" |
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| Title: Re: Does a radio signal at the frequency of light generate light or an EM wave? |
01 Apr 2005 11:51:53 AM |
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<guskz@hotmail.com> wrote in message
news:1112376965.781659.268090@z14g2000cwz.googlegroups.com...
I did not know that electromagnetic radio waves were a form of photon
(perhaps a photon vibrating at a different frequency?); I thought they
were electrons transmitted through the air or space.
I was wondering if one generates a radio signal at the frequency of
light, does it generate light or only a radio electromagnetic wave?
And are these waves, wether light or electromagnetic waves, harmfull to
the body or eyes (similar to gamma and x-rays)?
If it does generate light then is it multi-directional ondulatory light
waves (from the antenna's tip into a circular wave that propagates
wider and wider from the point of transmission) or is it a light beam
(such as a laser or a lightning/static single beam = mono-directional)?
I might be totally mistaken but light is an electromagnetic wave. Photons
are the force carrier for the electromagnetic force.
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| User: "Uncle Al" |
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| Title: Re: Does a radio signal at the frequency of light generate light or anEM wave? |
01 Apr 2005 03:17:51 PM |
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wrote:
I did not know that electromagnetic radio waves were a form of photon
(perhaps a photon vibrating at a different frequency?); I thought they
were electrons transmitted through the air or space.
Idiot.
I was wondering if one generates a radio signal at the frequency of
light, does it generate light or only a radio electromagnetic wave?
Idiot.
And are these waves, wether light or electromagnetic waves, harmfull to
the body or eyes (similar to gamma and x-rays)?
[snip]
Camp out under a megawatt transmitter tower and get back to us.
--
Uncle Al
http://www.mazepath.com/uncleal/
(Toxic URL! Unsafe for children and most mammals)
http://www.mazepath.com/uncleal/qz.pdf
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| User: "Randy Poe" |
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| Title: Re: Does a radio signal at the frequency of light generate light or an EM wave? |
01 Apr 2005 12:03:02 PM |
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wrote:
I did not know that electromagnetic radio waves were a form of photon
(perhaps a photon vibrating at a different frequency?);
Uh, sort of.
Light is a form of electromagnetic radiation, and
so is radio. The classical description of EM radiation
is a propagating wave consisting of oscillating
electric and magnetic fields.
The modern description of EM radiation is that it is
quantized into photons.
Viewed as a classical wave, radio is an EM wave of
a lower frequency (roughly 10^7-10^9 Hz for most
applications) than visible light (on the order of
10^14 Hz).
I thought they
were electrons transmitted through the air or space.
No. Electrons are charged, have mass, and move at
speeds less than c. EM radiation is uncharged,
massless, and moves at c (in vacuum).
I was wondering if one generates a radio signal at the frequency of
light, does it generate light or only a radio electromagnetic wave?
We don't yet have circuits that oscillate at those
kinds of frequencies, but we are getting closer all
the time. A "radio" oscillating at 10^14 Hz would put
out a signal in the form of light.
And are these waves, wether light or electromagnetic waves, harmfull
to
the body or eyes (similar to gamma and x-rays)?
Light IS EM radiation. Is light harmful to the eyes?
Some radio frequencies are harmful, the frequencies used
in microwave ovens. They'd cook you just as well if emitted
by an antenna as they would in an oven.
If it does generate light then is it multi-directional ondulatory
light
waves (from the antenna's tip into a circular wave that propagates
wider and wider from the point of transmission) or is it a light beam
(such as a laser or a lightning/static single beam =
mono-directional)?
The pattern would depend on the antenna, just as with
radio transmission. Both scenarios are possible, but
it's not just the tip that transmits in the case of
an omni-directional antenna.
- Randy
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| User: "Tom Roberts" |
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| Title: Re: Does a radio signal at the frequency of light generate lightor an EM wave? |
02 Apr 2005 09:27:04 AM |
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wrote:
I did not know that electromagnetic radio waves were a form of photon
(perhaps a photon vibrating at a different frequency?);
Yes. Gamma rays, X rays, ultraviolet light, visible light, infrared
light, and all the different classifications of microwaves and radio
(SHF, UHF, VHF, HF, LF, VLF, ...) are described similarly by a single
theory: QED. And its wave and geometrical optics approximations. In
particular, single photon detection is possible for gamma, X, UV,
visible, and infrared radiation (the latter two require the detector be
cooled to ~12 K, because at higher temperatures any object emits
infrared radiation).
VLPCs (visible light photon counters) are a commercial product, and are
now common in large quantities (>4,000) in high-energy physics detectors
(they are typically connected to scintillating fibers). We also use
phototubes (which are far older, but don't work very well below green,
and not at all for infrared).
I thought they
were electrons transmitted through the air or space.
Good heavans, no. That would be a current (a spark or arc in free space).
I was wondering if one generates a radio signal at the frequency of
light, does it generate light or only a radio electromagnetic wave?
They are one and the same. But the techniques used to generate radio
waves (vacuum tubes or transistors connected to an antenna) don't work
at infrared or visible frequencies (or above).
And are these waves, wether light or electromagnetic waves, harmfull to
the body or eyes (similar to gamma and x-rays)?
Yes and no. This depends strongly on their frequency. See above.
Basically infrared and below are insufficiently energetic to ionize the
atoms in your body, and such radiation is relatively benign, compared to
more energetic radiation that can (and does) ionize atoms in your body
(thus damaging it -- this is one source of those "free radicals" you've
heard so much about).
If it does generate light then is it multi-directional ondulatory light
waves (from the antenna's tip into a circular wave that propagates
wider and wider from the point of transmission) or is it a light beam
(such as a laser or a lightning/static single beam = mono-directional)?
That depends on the details of the source -- a light bulb and a laser
both generate visible light, but the properties of the light are VERY
different.
Tom Roberts tjroberts@lucent.com
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| User: "PD" |
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| Title: Re: Does a radio signal at the frequency of light generate light or an EM wave? |
01 Apr 2005 03:39:19 PM |
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wrote:
I did not know that electromagnetic radio waves were a form of photon
(perhaps a photon vibrating at a different frequency?);
yes
I thought they
were electrons transmitted through the air or space.
no. That would be lightning.
I was wondering if one generates a radio signal at the frequency of
light, does it generate light or only a radio electromagnetic wave?
Electromagnetic waves at the frequency of visible light are visible
light. At lower frequencies, infrared. At lower frequencies, microwave.
At lower frequencies, shortwave. At lower frequencies, radio.
And are these waves, wether light or electromagnetic waves, harmfull
to
the body or eyes (similar to gamma and x-rays)?
It's a matter of degree. The short answer is that only light of a
certain frequency and above can ionize atoms (chiefly water, in
humans). Radio cannot do that.
If it does generate light then is it multi-directional ondulatory
light
waves (from the antenna's tip into a circular wave that propagates
wider and wider from the point of transmission) or is it a light beam
(such as a laser or a lightning/static single beam =
mono-directional)?
Lightning is not light traveling from cloud to ground or vice versa. It
is electric current. It gives off light in all directions, which is why
you can see lightning from all directions.
The shape of the light wave depends a lot on the emitter. Consider a
flashlight or a lighthouse, for example, neither of which is a laser.
Usually radio transmitters are designed to radiate in all (horizontal)
directions, but they don't have to be. They could be designed like
flashlights if you wanted to; but they'd be a lot bigger.
PD
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| User: "" |
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| Title: Re: Does a radio signal at the frequency of light generate light or an EM wave? |
01 Apr 2005 04:33:06 PM |
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wrote:
I did not know that electromagnetic radio waves were a form of photon
(perhaps a photon vibrating at a different frequency?); I thought
they
were electrons transmitted through the air or space.
I was wondering if one generates a radio signal at the frequency of
light, does it generate light or only a radio electromagnetic wave?
And are these waves, wether light or electromagnetic waves, harmfull
to
the body or eyes (similar to gamma and x-rays)?
If it does generate light then is it multi-directional ondulatory
light
waves (from the antenna's tip into a circular wave that propagates
wider and wider from the point of transmission) or is it a light beam
(such as a laser or a lightning/static single beam =
mono-directional)?
Peter K...
I'm confused--your other posts under "Peter K" would lead me to believe
you're well past this question in your thinking and logic. What's up?
Don't stand so close to your microwave when attemping to see the
"light" photons. My guess is the microwave won't be operating between
3.8-7.7x10^14 Hz.
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| User: "Guy Gordon" |
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| Title: Re: Does a radio signal at the frequency of light generate light or an EM wave? |
01 Apr 2005 10:36:04 PM |
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wrote:
I was wondering if one generates a radio signal at the frequency of
light, does it generate light or only a radio electromagnetic wave?
Yes, light is just a very high frequency electromagnetic wave.
And are these waves, wether light or electromagnetic waves, harmfull to
the body or eyes (similar to gamma and x-rays)?
No. It's just light.
All of the phenomena you've mentioned are electromagnetic waves. The only
difference is the amount of energy they carry.
Radio < microwave < IR < Visible light < UV < X-Ray < Gamma
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| User: "" |
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| Title: Re: Does a radio signal at the frequency of light generate light or an EM wave? |
02 Apr 2005 04:51:57 PM |
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Ok Thanks
My major misconception was brought about mostly since the electron is
also the center of an electric & magnetic force field as it moves along
the wire which stop as the soon as the electron(electricity) stops
moving along the wire?
http://physics.ucsd.edu/~tmurphy/phys10/lectures/19_radio.PDF
From the web link (yellow square #3), I believe to sum it up they say:
1. when a charge(as opposed to a static charge) is in motion it
produces a magnetic field (actually it should produce both E&M fields)?
2. and a charge in acceleration produces EM waves(thus I believe what
they mean by produce is transmit EM Waves)?
Actually when a charge is in motion(#1 above), I believe it also
accelerates and decelerates = varies (current varies in DC or AC form)
in order to produce this motion therefore why isn't it also producing
waves as well as a field(is it because it's a small
acceleration/deceleration)?
3. Resonance produces the strongest transmission of EM waves thus from
#2's acceleration nescessity, a resonance(harmony) permits "better"
acceleration (thus stronger transmission?) than the usually normal
motion(conduction) of a charge in an electric wire or EM coil?
guskz@hotmail.com wrote:
I did not know that electromagnetic radio waves were a form of photon
(perhaps a photon vibrating at a different frequency?); I thought
they
were electrons transmitted through the air or space.
I was wondering if one generates a radio signal at the frequency of
light, does it generate light or only a radio electromagnetic wave?
And are these waves, wether light or electromagnetic waves, harmfull
to
the body or eyes (similar to gamma and x-rays)?
If it does generate light then is it multi-directional ondulatory
light
waves (from the antenna's tip into a circular wave that propagates
wider and wider from the point of transmission) or is it a light beam
(such as a laser or a lightning/static single beam =
mono-directional)?
.
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| User: "Bill Hobba" |
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| Title: Re: Does a radio signal at the frequency of light generate light or an EM wave? |
02 Apr 2005 10:35:41 PM |
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<guskz@hotmail.com> wrote in message
news:1112482317.894696.165040@l41g2000cwc.googlegroups.com...
Ok Thanks
My major misconception was brought about mostly since the electron is
also the center of an electric & magnetic force field as it moves along
the wire which stop as the soon as the electron(electricity) stops
moving along the wire?
Inside a source of EMF we have some process that moves electrons from the
positive pole to the negative. When we connect a wire to create a current
the electrons flow form the negative back to the positive where they are
again moved to the negative pole. Thus they do not stop. In AC current the
direction changes at a regular frequency - but the principle is the same.
http://physics.ucsd.edu/~tmurphy/phys10/lectures/19_radio.PDF
From the web link (yellow square #3), I believe to sum it up they say:
1. when a charge(as opposed to a static charge) is in motion it
produces a magnetic field (actually it should produce both E&M fields)?
Correct.
2. and a charge in acceleration produces EM waves(thus I believe what
they mean by produce is transmit EM Waves)?
That an accelerating charge produces EM waves is a still unresolved
problem - see
http://www.mathpages.com/home/kmath528/kmath528.htm
Actually when a charge is in motion(#1 above), I believe it also
accelerates and decelerates = varies (current varies in DC or AC form)
in order to produce this motion therefore why isn't it also producing
waves as well as a field(is it because it's a small
acceleration/deceleration)?
It does. They however may be so small we can not detect them.
3. Resonance produces the strongest transmission of EM waves thus from
#2's acceleration nescessity, a resonance(harmony) permits "better"
acceleration (thus stronger transmission?) than the usually normal
motion(conduction) of a charge in an electric wire or EM coil?
The phenomena of resonance does not produce EM waves.
Bill
guskz@hotmail.com wrote:
I did not know that electromagnetic radio waves were a form of photon
(perhaps a photon vibrating at a different frequency?); I thought
they
were electrons transmitted through the air or space.
I was wondering if one generates a radio signal at the frequency of
light, does it generate light or only a radio electromagnetic wave?
And are these waves, wether light or electromagnetic waves, harmfull
to
the body or eyes (similar to gamma and x-rays)?
If it does generate light then is it multi-directional ondulatory
light
waves (from the antenna's tip into a circular wave that propagates
wider and wider from the point of transmission) or is it a light beam
(such as a laser or a lightning/static single beam =
mono-directional)?
.
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| User: "" |
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| Title: Re: Does a radio signal at the frequency of light generate light or an EM wave? |
03 Apr 2005 02:54:14 PM |
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Bill Hobba wrote:
<guskz@hotmail.com> wrote in message
news:1112482317.894696.165040@l41g2000cwc.googlegroups.com...
Ok Thanks
My major misconception was brought about mostly since the electron
is
also the center of an electric & magnetic force field as it moves
along
the wire which stop as the soon as the electron(electricity) stops
moving along the wire?
Inside a source of EMF we have some process that moves electrons from
the
positive pole to the negative. When we connect a wire to create a
current
the electrons flow form the negative back to the positive where they
are
again moved to the negative pole. Thus they do not stop. In AC
current the
direction changes at a regular frequency - but the principle is the
same.
http://physics.ucsd.edu/~tmurphy/phys10/lectures/19_radio.PDF
From the web link (yellow square #3), I believe to sum it up they
say:
1. when a charge(as opposed to a static charge) is in motion it
produces a magnetic field (actually it should produce both E&M
fields)?
Correct.
2. and a charge in acceleration produces EM waves(thus I believe
what
they mean by produce is transmit EM Waves)?
That an accelerating charge produces EM waves is a still unresolved
problem - see
http://www.mathpages.com/home/kmath528/kmath528.htm
Actually when a charge is in motion(#1 above), I believe it also
accelerates and decelerates = varies (current varies in DC or AC
form)
in order to produce this motion therefore why isn't it also
producing
waves as well as a field(is it because it's a small
acceleration/deceleration)?
It does. They however may be so small we can not detect them.
3. Resonance produces the strongest transmission of EM waves thus
from
#2's acceleration nescessity, a resonance(harmony) permits "better"
acceleration (thus stronger transmission?) than the usually normal
motion(conduction) of a charge in an electric wire or EM coil?
The phenomena of resonance does not produce EM waves.
Bill
If not resonance, then what ingredients are used to "only" generate a
magnetic field (EM field) in a coil/wire as opposed to what ingredients
are use to generate transmission in this same coil/wire (EM waves)?
guskz@hotmail.com wrote:
I did not know that electromagnetic radio waves were a form of
photon
(perhaps a photon vibrating at a different frequency?); I thought
they
were electrons transmitted through the air or space.
I was wondering if one generates a radio signal at the frequency
of
light, does it generate light or only a radio electromagnetic
wave?
And are these waves, wether light or electromagnetic waves,
harmfull
to
the body or eyes (similar to gamma and x-rays)?
If it does generate light then is it multi-directional ondulatory
light
waves (from the antenna's tip into a circular wave that
propagates
wider and wider from the point of transmission) or is it a light
beam
(such as a laser or a lightning/static single beam =
mono-directional)?
.
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| User: "Bill Hobba" |
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| Title: Re: Does a radio signal at the frequency of light generate light or an EM wave? |
03 Apr 2005 11:26:06 PM |
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<guskz@hotmail.com> wrote in message
news:1112558054.149358.208860@l41g2000cwc.googlegroups.com...
Bill Hobba wrote:
<guskz@hotmail.com> wrote in message
news:1112482317.894696.165040@l41g2000cwc.googlegroups.com...
Ok Thanks
My major misconception was brought about mostly since the electron
is
also the center of an electric & magnetic force field as it moves
along
the wire which stop as the soon as the electron(electricity) stops
moving along the wire?
Inside a source of EMF we have some process that moves electrons from
the
positive pole to the negative. When we connect a wire to create a
current
the electrons flow form the negative back to the positive where they
are
again moved to the negative pole. Thus they do not stop. In AC
current the
direction changes at a regular frequency - but the principle is the
same.
http://physics.ucsd.edu/~tmurphy/phys10/lectures/19_radio.PDF
From the web link (yellow square #3), I believe to sum it up they
say:
1. when a charge(as opposed to a static charge) is in motion it
produces a magnetic field (actually it should produce both E&M
fields)?
Correct.
2. and a charge in acceleration produces EM waves(thus I believe
what
they mean by produce is transmit EM Waves)?
That an accelerating charge produces EM waves is a still unresolved
problem - see
http://www.mathpages.com/home/kmath528/kmath528.htm
Actually when a charge is in motion(#1 above), I believe it also
accelerates and decelerates = varies (current varies in DC or AC
form)
in order to produce this motion therefore why isn't it also
producing
waves as well as a field(is it because it's a small
acceleration/deceleration)?
It does. They however may be so small we can not detect them.
3. Resonance produces the strongest transmission of EM waves thus
from
#2's acceleration nescessity, a resonance(harmony) permits "better"
acceleration (thus stronger transmission?) than the usually normal
motion(conduction) of a charge in an electric wire or EM coil?
The phenomena of resonance does not produce EM waves.
Bill
If not resonance, then what ingredients are used to "only" generate a
magnetic field (EM field) in a coil/wire as opposed to what ingredients
are use to generate transmission in this same coil/wire (EM waves)?
Think of a tuned circuit in the positive feedback loop of an oscillator. The
fact it has a resonance at a particular frequency is what causes the
oscillator to oscillate at that frequency - it is not what causes EM
radiation. As another example think of what the brushes on an electric
drill do to your television reception. The hash created by the brushes
occurs across a wide frequency range which is why you will have problems on
most channels - without a resonant circuit all that happens is the EM
radiation is not necessarily emitted at a particular frequency.
Thanks
Bill
guskz@hotmail.com wrote:
I did not know that electromagnetic radio waves were a form of
photon
(perhaps a photon vibrating at a different frequency?); I thought
they
were electrons transmitted through the air or space.
I was wondering if one generates a radio signal at the frequency
of
light, does it generate light or only a radio electromagnetic
wave?
And are these waves, wether light or electromagnetic waves,
harmfull
to
the body or eyes (similar to gamma and x-rays)?
If it does generate light then is it multi-directional ondulatory
light
waves (from the antenna's tip into a circular wave that
propagates
wider and wider from the point of transmission) or is it a light
beam
(such as a laser or a lightning/static single beam =
mono-directional)?
.
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| User: "Randy Poe" |
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| Title: Re: Does a radio signal at the frequency of light generate light or an EM wave? |
03 Apr 2005 04:08:08 PM |
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wrote:
If not resonance, then what ingredients are used to "only" generate a
magnetic field (EM field) in a coil/wire as opposed to what
ingredients
are use to generate transmission in this same coil/wire (EM waves)?
First, let me correct your statement that an "EM field"
is equivalent to a "magnetic-only field".
Whenever you have changing electric fields you get
magnetic fields, and whenever you have changing magnetic
fields you get electric fields.
I think you're asking what is the difference between
a static field and a propagating field, and the answer
is: change. The extra ingredient you need to see
EM transmission of energy is change.
- Randy
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| User: "" |
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| Title: Re: Does a radio signal at the frequency of light generate light or an EM wave? |
06 Apr 2005 12:32:30 PM |
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Randy Poe wrote:
guskz@hotmail.com wrote:
If not resonance, then what ingredients are used to "only" generate
a
magnetic field (EM field) in a coil/wire as opposed to what
ingredients
are use to generate transmission in this same coil/wire (EM waves)?
First, let me correct your statement that an "EM field"
is equivalent to a "magnetic-only field".
Whenever you have changing electric fields you get
magnetic fields, and whenever you have changing magnetic
fields you get electric fields.
I think you're asking what is the difference between
a static field and a propagating field, and the answer
is: change.
The extra ingredient you need to see
EM transmission of energy is change.
- Randy
Ok but even an alternating circuit produces "change" (since it's
alternating thus varying) but that's not the difference between a field
and a transmission.
Actually they all transmit (known as interference) which is why most
wires need insulation/shielding.
Therefore is the only factor to transmit farther (that what normal
electric circuit wires produce) simply more juice (more power or
voltage) or something else as well like resonance?
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| User: "bz" |
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| Title: Re: Does a radio signal at the frequency of light generate light or an EM wave? |
06 Apr 2005 12:45:01 PM |
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wrote in news:1112808750.019163.131580
@l41g2000cwc.googlegroups.com:
Ok but even an alternating circuit produces "change" (since it's
alternating thus varying) but that's not the difference between a field
and a transmission.
Actually they all transmit (known as interference) which is why most
wires need insulation/shielding.
Most wires need insulation because they need to be kept from touching
other, nearby conductors.
Insulation does not stop an antenna wire from radiating.
By the way, most powerline wires are NOT insulated. If a storm knocks down
some poles and you see a 'guy wire' laying across your car DON'T touch it,
it is probably NOT a guy wire and it may be live.
Therefore
Since your assumptions were wrong, your therefore is also bad.
is the only factor to transmit farther (that what normal
electric circuit wires produce) simply more juice (more power or
voltage) or something else as well like resonance?
To transmit a signal efficiently, your antenna should be resonant at the
frequency in question and its feed impedence should match your transmitters
output impedence.
--
bz
please pardon my infinite ignorance, the set-of-things-I-do-not-know is an
infinite set.
bz+sp@ch100-5.chem.lsu.edu remove ch100-5 to avoid spam trap
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| User: "Randy Poe" |
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| Title: Re: Does a radio signal at the frequency of light generate light or an EM wave? |
06 Apr 2005 01:02:39 PM |
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wrote:
Randy Poe wrote:
Ok but even an alternating circuit produces "change" (since it's
alternating thus varying) but that's not the difference between a
field
and a transmission.
And these alternating fields in the circuit do produce
transmission, as you note below.
Actually they all transmit (known as interference) which is why most
wires need insulation/shielding.
Not just wires. The processor itself in a computer
radiates, pretty strongly. I've heard of security
demonstrations where people sat in parking lots and
monitored what was happening on a computer inside
the building.
The protection against this is to shield the whole
computer, and sometimes even the room the computer
sits in.
Therefore is the only factor to transmit farther (that what normal
electric circuit wires produce) simply more juice (more power or
voltage) or something else as well like resonance?
Yes, there is an effect which you could think of
as a resonance effect. When you're designing an
antenna, the relation between physical dimensions
and wavelength affects your efficiency very strongly.
There's also impedance matching. TV antennas,
cables, and tuning circuitry have impedance ratings
and if you don't match impedance, you get reflections
that give you signal losses.
This gets into antenna theory, which I know only as
one briefly-seen subject within electromagnetic theory.
Electrical engineers take whole courses in this
stuff.
- Randy
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| User: "bz" |
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| Title: Re: Does a radio signal at the frequency of light generate light or an EM wave? |
06 Apr 2005 01:27:45 PM |
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"Randy Poe" <poespam-trap@yahoo.com> wrote in news:1112810558.992164.101130
@z14g2000cwz.googlegroups.com:
Not just wires. The processor itself in a computer
radiates, pretty strongly. I've heard of security
demonstrations where people sat in parking lots and
monitored what was happening on a computer inside
the building.
Sharp transitions, as in the pulses on the computer's buss, have very high
frequency componentents. Those components radiate quite nicely from the
traces on the circuit boards.
The protection against this is to shield the whole
computer, and sometimes even the room the computer
sits in.
Computers and other electronic equipment is SUPPOSED to be designed to
prevent such radiation IF IT WILL CAUSE interference to nearby radio
communications.
Earlier computers were MUCH worse.
--
bz
please pardon my infinite ignorance, the set-of-things-I-do-not-know is an
infinite set.
bz+sp@ch100-5.chem.lsu.edu remove ch100-5 to avoid spam trap
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| User: "Tom Roberts" |
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| Title: Re: Does a radio signal at the frequency of light generate lightor an EM wave? |
06 Apr 2005 02:19:21 PM |
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Randy Poe wrote:
Not just wires. The processor itself in a computer
radiates, pretty strongly. I've heard of security
demonstrations where people sat in parking lots and
monitored what was happening on a computer inside
the building.
This only works if you can get close enough, and can isolate the signal
from a single computer. The demonstration I witnessed (with hundreds of
others at a computer security convention (in Maryland -- you get to
guess where (:-)) picked up radiation from the CRT screen, not the
processor or internal traces -- think about it and you'll realize this
is MUCH better for eavesdropping (knowing the 1s and 0s from hundreds of
computer traces all jumbled together is probably not useful at all). The
source and eavesdropper systems were separated by about 30 feet on
stage. This was ~15 years ago and the details are a bit sketchy in my
memory, but the eavesdropped video was fuzzy but readable....
Tom Roberts tjroberts@lucent.com
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| User: "Sue..." |
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| Title: Re: Does a radio signal at the frequency of light generate light or an EM wave? |
06 Apr 2005 01:48:39 PM |
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Randy wrote:
<< Whenever you have changing electric fields you get
magnetic fields, and whenever you have changing magnetic
fields you get electric fields. >>
I can comb my hair and use an electrical field to pick up
bits of paper. Is there a some way I can wave a permanent
magnet around and attract the bits of paper?
Sue...
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| User: "RG_RG" |
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| Title: Re: Does a radio signal at the frequency of light generate lightor an EM wave? |
06 Apr 2005 01:50:57 PM |
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Sue... wrote:
Randy wrote:
<< Whenever you have changing electric fields you get
magnetic fields, and whenever you have changing magnetic
fields you get electric fields. >>
I can comb my hair and use an electrical field to pick up
bits of paper. Is there a some way I can wave a permanent
magnet around and attract the bits of paper?
Sue...
If you charge the magnet, then yes.
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| User: "Sue..." |
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| Title: Re: Does a radio signal at the frequency of light generate light or an EM wave? |
06 Apr 2005 02:04:52 PM |
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LOL
;-)
Sue...
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| User: "Randy Poe" |
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| Title: Re: Does a radio signal at the frequency of light generate light or an EM wave? |
03 Apr 2005 04:10:18 PM |
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wrote:
Ok Thanks
My major misconception was brought about mostly since the electron is
also the center of an electric & magnetic force field as it moves
along
the wire which stop as the soon as the electron(electricity) stops
moving along the wire?
Because electrons or any charge distribution produce
an electric field, moving electrons can be used to
produce a magnetic field.
That's not the only way to produce either an electric
or a magnetic field.
It's like assuming that because trumpets produce sound,
then all sound is produced by trumpets.
- Randy
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