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Author Topic: Can photons be cancelled out like audible noise?  (Read 2254 times)

Offline stu

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Can photons be cancelled out like audible noise?
« on: 11/09/2012 01:55:18 »
Can a photon of light,or many in an area be visibly cancelled out in the same manner that sound cancelling headphones do their job

eg

using a inverse frequency or anti photon?

« Last Edit: 11/09/2012 21:44:07 by chris »


 

Offline syhprum

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Re: photon control
« Reply #1 on: 11/09/2012 06:36:52 »
If two sources of photons of the same frequency meet an interference pattern is set up with peaks and troughs' you can notice this when driving your car while listening to the radio from two synchronised transmitters you will find that there are places where the signal disappears when you hit a null spot.
Before the advent of GPS various systems were setup using this effect for navigation purposes
« Last Edit: 11/09/2012 06:47:55 by syhprum »
 

Offline stu

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Re: photon control
« Reply #2 on: 11/09/2012 06:55:42 »
This is radio waves, much lower frequency. Can the same be applied thru the em spectrum.

Does the perpendicular em wave  apply all the way thru
 

Offline syhprum

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Re: photon control
« Reply #3 on: 11/09/2012 10:00:44 »
Yes indeed the same thing happens at any frequency all electromagnetic radiaton is the result of photons.
 

Offline lightarrow

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Re: photon control
« Reply #4 on: 11/09/2012 12:36:13 »
If two sources of photons of the same frequency
Two coherent sources of photons. If there isn't a definite relation of phase between the two, you don't have interference.
 

Offline evan_au

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Re: photon control
« Reply #5 on: 11/09/2012 12:46:31 »
Cancellation by a light source by interference mostly results in areas of low intensity (nulls) that are smaller than a wavelength. For an AM radio transmitter, this may be a few hundred yards, but for visible light, they are usually invisibly small.

Interference also works best for coherent light of a single frequency; most light sources have a wide frequency spectrum (especially tungsten light filaments) - this is hard to cancel.

Noise-cancelling headphones use the fact that electronics works at speeds far higher than the speed of sound, so it can produce an anti-noise signal at the same time as the noise signal. Good luck measuring and processing visible light faster than light!

The best way to keep photons out of a larger area is to use a mirror, or a black cloth!

There have been some experiments with materials having a "negative index of refraction" that can wrap light around small objects, but they usually work only in a narrow frequency band.
 

Offline stu

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Re: photon control
« Reply #6 on: 11/09/2012 13:29:26 »
Thanks guys

I wasnt thinking about processing the light ,more about using a distance trap in method of inversion to reflect it back on itself ,as its frequency is so high should make it shouldnt need much distance to shift by half a phase

self regulating to whatever frequency came in ,would go out,just delayed by having to travel the nano second further then back onto itself

oversimplified I know

just pondering.  Appreciate the input

 

Offline evan_au

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Re: Can photons be cancelled out like audible noise?
« Reply #7 on: 13/09/2012 13:00:19 »
Mirrors work a bit like what you said - the incoming electromagnetic wave induces a corresponding wave in the conductor of the mirror, interfering with the incoming wave and producing an outgoing wave.

"The angle of incidence = the angle of reflection", like we learned in High School.
 

Offline JP

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Re: Can photons be cancelled out like audible noise?
« Reply #8 on: 13/09/2012 17:53:22 »

self regulating to whatever frequency came in ,would go out,just delayed by having to travel the nano second further then back onto itse


Things like this are done in interferometry.  Generally the goal isn't to cancel things out, but to make the light that has taken two paths interfere with itself, rendering any variations in path length between the two paths visible in interference patterns. 

The trick is that light wavelength is tiny (~500 nanometers), so setting up things at just the right distances can be extremely tricky.  Even slight mechanical vibrations can throw things off.
 

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Re: Can photons be cancelled out like audible noise?
« Reply #8 on: 13/09/2012 17:53:22 »

 

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