Double Slit Experiment

[InfiniteNow]

If you change the frequency of photons being fired through the slits, does the interference pattern change as well?

Another strange thing is that even if you fire a single photon at a time through the slits, and track where each lands on the screen, letting a pattern build up like splattered paint (usually using computer modelling)... although they are going through one at a time... blip blip blip blip... they will start to build what looks like an interference pattern with waves (crests and troughs).

 

With what are the photons interfering if they are being fired one at at time? Oyyy...

[EWright]

Another strange thing is that even if you fire a single photon at a time through the slits, and track where each lands on the screen, letting a pattern build up like splattered paint (usually using computer modelling)... although they are going through one at a time... blip blip blip blip... they will start to build what looks like an interference pattern with waves (crests and troughs).

 

With what are the photons interfering if they are being fired one at at time? Oyyy...

 

Is this theoretical, or CAN we actually fire one photon at a time? Has that specifically been done? And does the look of the interference pattern change relative to the frequency of the photon(s) used?

[InfiniteNow]

Is this theoretical, or CAN we actually fire one photon at a time? Has that specifically been done? And does the look of the interference pattern change relative to the frequency of the photon(s) used?

No

Yes

Yes

Not sure

[CraigD]

Is this theoretical, or CAN we actually fire one photon at a time? Has that specifically been done?

Yes to all questions.

 

It’s not particularly difficult to fire, on average, only one photon in a particular frequency range (in the case of the double slit experiment, one that the photographic film is sensitive to) in a particular time interval. Something as simple as smoked glass filters and an ordinary light bulb can be used.

And does the look of the interference pattern change relative to the frequency of the photon(s) used?

Very much so. Try making a dual slit apparatus that shines on plain white paper (big cardboard tubes are handy for making these), wait for night, and examine the patterns for various streetlights and signs – handy sources of narrow-spectrum light. (the same apparatus with only a single slit produces nice-to-look-at specra, though no light/dark interference pattern)

 

Or, if you prefer thought experiments and paper doodling, consider an interference pattern due to ocean waves passing through 2 “slits” in a breakwater.

[EWright]

Yes to all questions.

Try making a dual slit apparatus that shines on plain white paper (big cardboard tubes are handy for making these), wait for night, and examine the patterns for various streetlights and signs – handy sources of narrow-spectrum light. (the same apparatus with only a single slit produces nice-to-look-at specra, though no light/dark interference pattern)

 

Or, if you prefer thought experiments and paper doodling, consider an interference pattern due to ocean waves passing through 2 “slits” in a breakwater.

 

I see no reason two seperate ocean waves would cancel each other while passing through two separate slits, which are separated by space and time.

 

I have read about the experiment before, just haven't given it much thought lately... but i am skeptical of the reasoning for it.

 

If you keep the setup the same, and then remove the partition between the splits, what happens and why?

[InfiniteNow]

Or, if you prefer thought experiments and paper doodling, consider an interference pattern due to ocean waves passing through 2 “slits” in a breakwater.

(Referencing Post #35...)

 

 

So let's say somehow one drop of water at a time reaches the slits, and you saw an interference pattern on the other side. How does this happen? What is the single drop (photon) interfering with? :Waldo:

[CraigD]

So let's say somehow one drop of water at a time reaches the slits, and you saw an interference pattern on the other side.

You won’t. Water has be in wave form to produce interference patterns – making it into drops and throwing it won’t produce them.

 

(Actually, if you can make the drops small enough and throw them slowly enough, it can, but on the scale of its associated De Broglie wave. I don’t believe the feat has been managed with anything much bigger than hydrogen nuclei)

[EWright]

(Referencing Post #35...)

 

 

So let's say somehow one drop of water at a time reaches the slits, and you saw an interference pattern on the other side. How does this happen? What is the single drop (photon) interfering with? :Waldo:

 

By George! Is it possible the energy of the photons "splashes" when it hits the film in such a way that the combined effects create an interference pattern? Or... is it possible that these "splashes" energize the film in such a way as to cause a pattern of 'magnetic' resistant areas (similar to opposite ends of a magnet rejecting each other, or electrons spacing themselves at equal distances?)

[InfiniteNow]

You won’t. Water has be in wave form to produce interference patterns – making it into drops and throwing it won’t produce them.

 

(Actually, if you can make the drops small enough and throw them slowly enough, it can, but on the scale of its associated

De Broglie wave

. I don’t believe the feat has been managed with anything much bigger than hydrogen nuclei)

But that's just it... this is EXACTLY what happens when light is passed through the slits one photon at a time.

[EWright]

But that's just it... this is EXACTLY what happens when light is passed through the slits one photon at a time.

 

I've heard of one electron at a time still causing an interference pattern, which would be more akin to the water droplets. Can someon e point me to info on an actual experiemtn using one Photon at a time?

[Qfwfq]

The single photon interference is a classic 20th century experiment that has been done many times, it's the one I chose with a couple of friends for 4th year lab.

 

Interference has been observed for molecules too, even fairly large ones.

 

The single object interferes with itself.

[InfiniteNow]

Single Photon Interference (from http://www.fas.harvard.edu)

[EWright]

Single Photon Interference (from http://www.fas.harvard.edu)

 

Please not the comments section of your site... it seems these are electrons afterall.

Strictly speaking, we are not detecting single photons of light but rather single photoelectrons, liberated by the light impinging on the detector screen. Nevertheless, the quantum nature of light is evident.

[Qfwfq]

That's only how the photons are detected.

[EWright]

That's only how the photons are detected.

 

Ah, I was under the impression that the photoelectrons were generated within the firing apparatus. Still, I can't help but feel something is lost in the translation when it comes to the single photon/electron interference patterns.

[Abstruce]

No need to use so much bold Abstruce, please don't get upset if you disagree with someone..

 

Sorry, I was using bold to differentiate between the actual text describing the Schrödinger's Cat experiment. I did not use it as a form of expression, only to differentiate between statements. And no I was not yelling.

 

 

The matter is certainly not a fairy tale for objects that can be in a coherent state, experiments have even been done on many-atom objects but not quite the size of a cat. In the macroscopic world quantum formalism applies but decoherence rapidly rushes in to dominate.

 

Suppose the autopsy determines the cat as being dead since ten minutes after closing the box, which remained closed for an hour. If it weren't for decoherence one could say that's one of the many component states the cat was in. To be precise, in fact, the states "dead" and "live" would each be categories of states. When the box has been opened but the autopsy hasn't yet been performed, the cat would still be in a superposition of many different states of the "dead" category. Again, that's if it weren't for decoherence.

[InfiniteNow]

Please not the comments section of your site... it seems these are electrons afterall.

Yeah, I saw that, but please note this was only ONE of thousands of articles. I liked this one b/c it also showed how to set it up.

 

 

What I want to figure out (or, at least discuss here) is how a single photon interferes with itself, a phenomenon which has been shown and replicated frequently. I'm stumped... :hihi: