Light, RF and Space

Willen · Sep 26, 2015

I am going to ask some fundamental questions of physics:

1) Light and RF has equal speed, does it mean that the light and RF are totally similar mechanism? (distinguish)

2) Light also has wavelength, does it mean it has sine wave signal? And source of light is like a high frequency oscillator, like the Sun, candle, LED etc?

Will ask some other questions (about space etc) after getting concept of these two questions. It would be very nice information to understand many more things.
I am not a native speaker of English and I am not from academic engineering, science field. So basic and easy elaboration needed.

nsaspook · Sep 26, 2015

1) Light and RF are just names for electromagnetic waves of different frequencies.
2) Electromagnetic waves are usually described using sine wave signals but it's not a requirement nor is necessary to explain electromagnetic wave propagation in space.

Classic electromagnetic waves are the product of charge movements in matter. A single isolate point charge can create an EM wave but usually there are many charges in motion that might be somewhat random like we see in a candle light or more synchronized like you would see in a laser diode.

Willen · Sep 27, 2015

If Light is also an electromagnetic wave with frequency then can we detect wave of light with suitable metal antenna? And also the light created by candle, wood is an electromagnetic (electricity+magnet)? Sounds interesting to me.

Or can we get slower signal (like MHz or KHz) of the light by dividing its frequency in great amount, lets say with extremely fast device.

JoeJester · Sep 27, 2015

Look up the frequency of light, then determine the wavelength of the suitable antenna.

nsaspook · Sep 27, 2015

Willen said:
If Light is also an electromagnetic wave with frequency then can we detect wave of light with suitable metal antenna? And also the light created by candle, wood is an electromagnetic (electricity+magnet)? Sounds interesting to me.

The size needed for a metal antenna for light is tiny but with modern nanotechnology we can build dipole metal antennas for light to directly capture electrical energy. When you see the light reflected from a mirror the thin metal coating is reflecting the light image with the similar effect of an RF antenna reflector.

Yes, they are all EM waves and the electricity+magnet concept is like this:

The are never ever seperated, sometimes one side or the other dominates but they are one. EM waves are one method the universe has to transmit changes from one part of space to another part of space. If a charged particle moves, the 'electric' force of the particle on other particles is sent by EM waves.

Willen · Sep 27, 2015

JoeJester said:
Look up the frequency of light, then determine the wavelength of the suitable antenna.

Hi, Always I have found the wavelength of light instead of frequency of light. Wavelength maybe around nanometer (depends of colors of light maybe). Can we express the frequency of light in words/numbers?

nsaspook said:
The size needed for a metal antenna for light is tiny but with modern nanotechnology we can build dipole metal antennas for light to directly capture electrical energy.

Solar panel (photocell) generates electricity based in the theory exactly as your are saying here, by capturing electrical energy of the light directly?

EM waves are one method the universe has to transmit changes from one part of space to another part of space. If a charged particle moves, the 'electric' force of the particle on other particles is sent by EM waves.

Now it's a turn to ask about space: Universe has no limitation about its size. Space is totally empty (no gas, no humidity, no cloud, no air). Then why sun cannot send its light to FAR..........universe? Why we cannot get light from extremely huge stars at night like the sun? Actual question is what is the thing that blocks light and RF in space after certain distance?

Les Jones · Sep 27, 2015

To convert wavelength to frequency divide the wavelength (In units of meters) into 300 and the result is the frequency in MHZ . The sun (And other stars.) can send it's light over very long distances but the intensity diminishes rapidly. The intensity of the light (Or any other electromagnetic waves,) diminishes by the inverse square law. Consider a point source and the intensity at 1 metre from it. The energy will be spread over the surface of a sphere with a radius of 1 metre. (Area 4PiR^2 = 12.57 sq metres) If we are now 10 metres from the source the energy is now spread over a sphere wit a radius of 10 metres. so the same amount of power is spread over an area of 1257.0 sq metres so it's intensity is one hundredth of what it was at 1 metre from the source. So you can see that the intensity diminishes rapidly with distance.

Les.

nsaspook · Sep 27, 2015

Willen said:
Solar panel (photocell) generates electricity based in the theory exactly as your are saying here, by capturing electrical energy of the light directly?

Today's solar panels don't use light as an EM wave to generate electricity, panels use the particle nature of light with semiconductors to generate electricity.
http://hyperphysics.phy-astr.gsu.edu/hbase/mod1.html

KeepItSimpleStupid · Sep 28, 2015

the OP said:
Hi, Always I have found the wavelength of light instead of frequency of light. Wavelength maybe around nanometer (depends of colors of light maybe). Can we express the frequency of light in words/numbers?

See: https://www.google.com/search?q=em+...DrVrQ-cOM:&usg=__vx8wSgjmBHpecDe0isdYlpQVpww=

So, we can give it a color. Think crayons.

I learned the wavelengths in Angstroms, but now nanometers is preferred. ROY G. BIV Red, orange Green, Blue, Indigo, Violet is the general acronym for the spectrum order.

You can also think about "Color temperature"

https://www.google.com/search?q=em+...oE6urHhCM:&usg=__vx8wSgjmBHpecDe0isdYlpQVpww=

You can separate light with a monochometer.

And sunlight has some standard compositions associated with it. https://www.pveducation.org/pvcdrom/appendices/standard-solar-spectra, but it's not constant.

All colors give you a "white" light. No colors, you get black. When your dealing with a "white" light source, "color temperature" is a better way to describe it.

https://en.wikipedia.org/wiki/Monochromator

nsaspook · Sep 28, 2015

A little meat on the EM Yang/Yin
https://www.feynmanlectures.caltech.edu/II_13.html

It turns out that any inertial frame will do. We will also see that magnetism and electricity are not independent things—that they should always be taken together as one complete electromagnetic field. Although in the static case Maxwell’s equations separate into two distinct pairs, one pair for electricity and one pair for magnetism, with no apparent connection between the two fields, nevertheless, in nature itself there is a very intimate relationship between them that arises from the principle of relativity. Historically, the principle of relativity was discovered after Maxwell’s equations. It was, in fact, the study of electricity and magnetism which led ultimately to Einstein’s discovery of his principle of relativity. But let’s see what our knowledge of relativity would tell us about magnetic forces if we assume that the relativity principle is applicable—as it is—to electromagnetism.

nsaspook · Oct 1, 2015

https://www.prosoundtraining.com/si...ng-electricity-means-understanding-the-field/

“The usually accepted view that the conductor current produces the magnetic field surrounding it must be displaced by the more appropriate one that the electromagnetic field surrounding the conductor produces, through a small drain on the energy supply, the current in the conductor. Although the value of the latter may be used in computing the transmitted energy, one should clearly recognize that physically this current produces only a loss and in no way has a direct part in the phenomenon of power transmission.”

“There it was, right in front of me in black and white! The current does not flow around a loop setting up a magnetic field as I had, along with countless other engineers, been taught in high school and university. It is the other way round. The electric current is but an artifact of a more fundamental entity.”

Willen · Oct 1, 2015

Hi again,
As I understand intensity of light (lets say- of the sun) goes weak due to spreading its waves around space and at last it cannot be seen from far universe. Is it a only one reason so that the light disappears in free space?

Then same thing happens to RF? What are the obstacles of RF in free space? Probably we could get more range from simple RF transmitter in space than the earth. (eg- in earth; wet earth, buildings, clouds, hills...are the obstacles of RF)

nsaspook · Oct 1, 2015

Willen said:
Hi again,
As I understand intensity of light (lets say- of the sun) goes weak due to spreading its waves around space and at last it cannot be seen from far universe. Is it a only one reason so that the light disappears in free space?

Then same thing happens to RF? What are the obstacles of RF in free space? Probably we could get more range from simple RF transmitter in space than the earth. (eg- in earth; wet earth, buildings, clouds, hills...are the obstacles of RF)

Each photon of EM energy will exist the until it interacts with matter so it won't disappear but the ability to detect it (the energy flux) uniquely from all the other random photons of energy will turn it to random noise instead of a signal. There are several ways in nature to concentrate EM energy into beams (like lasers) that don't obey a simple free-space path loss https://en.wikipedia.org/wiki/Free-space_path_loss#Free-space_path_loss_formula

One way is what's suspected with Pulsars. The suns are suspected to be a superluminal light source. This does NOT mean the light travels faster than c from the star to earth. It only means the method of generation involves properties of electricity that can change FTL are involved and these changes are consistent with the known theories of Special Relativity.
https://www.universetoday.com/49646/faster-than-light-pulsar-phenomena/

Observational data from nine pulsars, including the Crab pulsar, suggest these rapidly spinning neutron stars emit the electromagnetic equivalent of a sonic boom, and a model created to understand this phenomenon shows that the source of the emissions could be traveling faster than the speed of light. Researchers say as the polarization currents in these emissions are whipped around with a mechanism likened to a synchrotron, the sources could be traveling up to six times light speed, or 1.8 million km per second. However, although the source of the radiation exceeds the speed of light, the emitted radiation travels at normal light speed once it leaves the source. “This is not science fiction, and no laws of physics were broken in this model,” said John Singleton of Los Alamos National Laboratory at a press briefing at the American Astronomical Society meeting in Washington, DC. “And Einstein’s theory of Special Relativity is not violated.”

People are working to develop RF technologies based on this principle.

Though a radiation source that exceeds the speed of light may sound like a violation of Special Relativity, the universal speed limit does not apply to a polarization current, since the carrier of the current is a pattern of electric polarization, rather than charged particles [4, 11, 12]. Such a pattern may be made to move faster than light by the coordinated subluminal motion of charged particles [11]. No laws of physics are broken and Maxwell’s equations, which are necessarily relativistic, can be used to predict the emitted radiation [4, 12].

https://laacg.lanl.gov/superluminal/pubs/DRsummary.pdf

The situation becomes even more unusual when the superluminal source also accelerates. Fig. 2b shows a superluminal source moving in a circle; here, the acceleration is centripetal [4, 12]. The Huygens wavelets now form a Cerenkov envelope consisting of an asymmetric two- ˇ sheet structure. It is relatively simple to show that an observer within the envelope will see an odd number (3, 5, 7. . . ) of images of the source (i.e., an odd number of retarded times), the exact number depending on the source speed [3]. The most remarkable effect, however, occurs where the two sheets meet tangentially on a cusp curve (Fig. 2b); an observer at this point will receive instantaneously contributions from an extended period of source time [2, 4, 12]. This unique effect, demonstrated experimentally by the machine shown in Fig. 1 [1, 2], represents focusing of radiation in the time domain to produce a concentration of electromagnetic energy. The initial work indicates that this temporal focusing has possible applications in radar [8] and long-range, low-power, secure communications. A related effect occurs when a source undergoes linear acceleration (Fig. 2c); here, there is an extreme concentration of emitted radiation caused by temporal focusing in a ring around the source’s path [13]. Our studies suggest directed energy applications for such a source.

Willen · Oct 2, 2015

Hi again,
it seems interesting!
1) How can I understand 'photons' and 'particles' (in very simple terms please)? We cannot see EM but we can see light, or not?

2) According to inverse law of square, light emitted by the Sun (or stars) disappears never? And goes to far and far and far........universe by spreading and spreading? Then probably the light of my small tourch is also able to travel millions of kilometers far way! Amazing!

misterT · Oct 2, 2015

nsaspook said:
1) Light and RF are just names for electromagnetic waves of different frequencies.

So, does radio signals have the same dual nature than light? Does the classic "double slit experiment" work the same way with light and radio signals? What about circular polarization.

nsaspook · Oct 2, 2015

misterT said:
So, does radio signals have the same dual nature than light? Does the classic "double slit experiment" work the same way with light and radio signals? What about circular polarization.

Yes, they do as a photon is a photon but the scale of the experiment would be huge at low frequencies.
You can say the 'size' of the photon is a function of the particle's "wavelength" when considered as a wave in the framework of the distance another particle could interact with this particle with respect to the bandwidth of the signal to be detected. A simple example:
We have a radio signal with a wavelength of 1 meter and we need a bandwidth of 1/10 of the wave frequency to detect a signal. The photon 'size' would be about 10X wavelengths or ten meters. It's all pretty strange and weird to look at an rf EM wave as a photon.
https://en.wikipedia.org/wiki/Coherent_states

Electromagnetic waves are the photons and circular polarization is just a propagation mode of those waves.

https://www.space.com/667-quantum-astronomy-cosmic-scale-double-slit-experiment.html

Light, RF and Space

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