I think this article sheds some light on the question. You need a material with a negative magnetic permeability to conduct EM in the terahertz range.

http://en.wikipedia.org/wiki/Terahertz_metamaterials

John

 

Is there a maximum possible physical frequency, at which point the wavelength is equal to the Planck length?
And would any radiation with a smaller wavelength than that have to be going faster than light?
(obviously we cant create radiation that extreme)

 

You can not go faster than light, and frequency is not a speed. The question about wavelength is a good one. As far as I know the highest energy photons are created by black holes, I suspect that is an upper limit.

I'm not sure how meta materials (which can be made for any frequency of EM radiation) can be used to say EM radiation and photons are different. It does not follow.

 

You can not go faster than light, and frequency is not a speed.

sorry, I was mushing the two together, speed is always c

what I was asking was that if you were to create a wave with a frequency higher than the frequency at which the wavelength is the planck length, it would either have to start going faster than the standard c, or it would have to exist in an area smaller than that of the planck length, correct?

Because c may not be a speed limit when lengths less than the planck length or times less than the planck time are involved, such as the very beginning of the big bang?
(is a photon an EM wave only one wavelength long? like a segment of the wave created by a current carrying wire?)

The question about wavelength is a good one. As far as I know the highest energy photons are created by black holes, I suspect that is an upper limit.

But what about black holes with a mass less than the planck mass (and therefore diameter less than the planck lenght)?
can they even exist?
could they release radiation beyond these limits?
If they can't exist, why are people worried about particle accelerators creating black holes?

Ima do some quick maths and see what the maximum frequency should be...

[EDIT]
alright, using 299792458m/s divided by 1.616252e-35m I got 1.8548621e43 Hz
or 18548621000000000000000000000000000000000000Hz, or 18548621000000000000YHz, essentially really big

 

Hey, since the wavelength of radiation is decreased in a medium, and the denser the medium the more the wavelength is decreased, and lower frequencies can go through denser things easier, could this play a role?

 

All I really know and think is you have to take each frequency on a case by case basis. 2.4 Gigahertz is useful for heating water (rotating molecules anyone?), and for a long time was a dominant frequency used in communications such long distance telephone and satellite dishes (neither is true anymore).

There is a new application for a millimeter wave that causes intense pain for people in the path. It activates the nerve endings and makes your skin feel like it is on fire. Nom Jabar anyone (Dune reference)?

 

All I really know and think is you have to take each frequency on a case by case basis. 2.4 Gigahertz is useful for heating water (rotating molecules anyone?), and for a long time was a dominant frequency used in communications such long distance telephone and satellite dishes (neither is true anymore).

I know, there really is no useful application for knowing what happens with electromagnetic radiation at the absolute extreme values possible, I'm just trying to figure out why things happen and how they happen and make a bit of sense of it all along the way.

There is a new application for a millimeter wave that causes intense pain for people in the path. It activates the nerve endings and makes your skin feel like it is on fire. Nom Jabar anyone (Dune reference)?

spicy

 

this is altogether a different question..but i thought i could ask it here..(you guys are very active)

How can a wire just connected to one end of an alternating source (or an o/p pin of a frequency transmitter) ever complete the circuit (refer image).it is only then ,due to the acceleration of electrons that a magnetic field is created??is this not an open circuit?but how do things work?

 

I don't think it's the current flowing as much as it is the change in voltage... also, the wire will have some capacitances and such that allow electrons to... do stuff
there are electrons flowing in and out of the wire at the AC source though, they just cant travel anywhere.

Someone else can probably explain it much better than me.

 

this is altogether a different question..but i thought i could ask it here..(you guys are very active)

How can a wire just connected to one end of an alternating source (or an o/p pin of a frequency transmitter) ever complete the circuit (refer image).it is only then ,due to the acceleration of electrons that a magnetic field is created??is this not an open circuit?but how do things work?

Are you talking RF transmission, as in antenna?

Your picture is way off. Look up dipole antennas in Wikipedia, the ends of the wire are the least active (radiative) area on the the antenna.

Part of the answer is antenna resonance. The signal bounces between the ends, because they have no termination. It the antenna is cut to length this bouncing back and forth is reinforced, and the signal radiates off the wire. That same resonance also means the wire is a good receiving antenna too.

 

brother Bill_marsden,
exactly,I do ask about R.F.Transmission.The thing I ve tried to draw is a dipole antenna founded by prof. Hertz. .I do not understand the concept of resonance.What I ask is when a current cannot flow in an open circuit,(in this pic,will any current flow through the wire C?no i suppose ..)how is an E.M.wave generated? and what resonates with respect to what?on seeing in wiki or in any text book,they either convince with some math or a colourful 3-D plot.

I cannot understand the generation and flow of an E.M wave the way i understand the flow of current in an electric circuit (analogous to the flow of water)

 

With the water flow analogy, some water is flowing in, and increasing the pressure in the pipe, and then some water flows out, and decreases the pressure in the pipe.

Water may not be able to do that easily, but electrons can. If it helps, think of it as air, since it's more easily compressible.

 

brother Bill_marsden,
exactly,I do ask about R.F.Transmission.The thing I ve tried to draw is a dipole antenna founded by prof. Hertz. .I do not understand the concept of resonance.What I ask is when a current cannot flow in an open circuit,(in this pic,will any current flow through the wire C?no i suppose ..)how is an E.M.wave generated? and what resonates with respect to what?on seeing in wiki or in any text book,they either convince with some math or a colourful 3-D plot.

I cannot understand the generation and flow of an E.M wave the way i understand the flow of current in an electric circuit (analogous to the flow of water)

If you think of the wire and air as conductors with an impedance that the EM fields travel and that the EM fields are always present when there is power flowing and not just created at the antenna it might be easier.

The antenna functions as a transformer to match the impedance of wiring side circuit to the free space impedance of a vacuum. The feed impedance of a full wave folded dipole is about 300 ohms and is a pretty good match for the space impedance.

http://en.wikipedia.org/wiki/Impedance_of_free_space
http://en.wikipedia.org/wiki/Twin-lead
http://www.radio-electronics.com/info/antennas/dipole/folded_dipole.php