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Basic Electronics » Electro-magnetism. Concept check.

July 12, 2011
by Hexorg
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Hey everyone, I just wanted to go over some basic concepts.

If I have a mathematically perfect oscillator, that can vibrate at any frequency, and I make a current pass through the wire at 545THz, will the wire start glowing green?

Also, if I have a fast enough, perfect oscilloscope, and I shine a green light at the probe, will I see a sine wave of 545THz?

I know that such switching speeds are impossible by any modern technology, but will the above happen if we did have fast and sensitive enough equipment?

July 12, 2011
by Noter
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The wire wouldn't glow at all unless it got hot enough to emit photons. Then it is probably the material that determines the color rather than the frequency that is used to heat it up.

Liekwise, wouldn't you have to shine the light on a material that will generate a voltage when bombarded with photons before you could have an electronic signal?

I don't know, just guessing.

July 12, 2011
by Hexorg
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Well I thought about that, because if you apply a 400Mhz voltage to a wire it starts emmiting 400Mhz electro-magnetic waves (Radio, cell phones, WiFi, etc...) So if you apply 545THz voltage, shouldn't it start emmiting 545THz electro-magnetic waves?

July 12, 2011
by bretm
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The resistance of the wire increases with frequency, due to the skin effect. This happens because of eddy currents caused by the rapidly changing magnetic field from the alternating current. The skin depth at 545 THz in copper would be about 3nm which is much smaller than the wavelength of light of the same frequency. That's a fancy way of saying "metal is opaque".

July 12, 2011
by Hexorg
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Noo bretm, you shattered my dreams! Lol thanks :D that's a cool thing to know :D

July 12, 2011
by Noter
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I suppose it would but you can't see electro-magnetic waves so there's no color or glow necessarily associated with it.

July 12, 2011
by Hexorg
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Noter, but visible light IS an electro-magnetic wave

July 12, 2011
by bretm
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Sorry! :-) That was a lot of hand-waving, though, and a gross oversimplification. There actually is a lot of research going on in terahertz oscillators. It's just more complicated than a high frequency in a wire because of the physics involved at those frequencies.

July 12, 2011
by Hexorg
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bretm, sounds like it's going to turn into something quantum-physics-like >_< haha

July 12, 2011
by Noter
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Well ok. I should have stuck with my first I don't know - LOL!

July 13, 2011
by mongo
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545 THZ? I'd like to see an oscillator do that first. A wire resonant to that frequency would be really really short.

July 13, 2011
by BobaMosfet
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hexorg, to specifically answer your questions, the answer is no, and no.

BM

July 13, 2011
by Robotnik
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well, I guess is you had an oscillator that COULD make 545 thz it would glow green... I think fastest alternating current so far is around 500 Ghz, but don't quote me on it cause I don't actually remember where I read that.

July 13, 2011
by BobaMosfet
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No, it would not glow green. There are energy transference issues, directional issues, and more. The great thing about postulating is you can suspend the laws of physics to do so- the problems with it is you suspend the laws of physics.

BM

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