Double slit experiment - sensor interacts with photons?

[gen x]

sensor in slit must interact with photon, so isn't sensor reason why patterns on screen change?
So what is exactly weird in this experiment?

Can we somehow observe photon in slit but do not physically interact with him?

 

[Matterwave]

What do you mean by sensor in slit? In the traditional double slit experiment there's no sensors in the slits.

 

[gen x]

What do you mean by sensor in slit? In the traditional double slit experiment there's no sensors in the slits.

How we observe photon?

 

[Nugatory]

sensor in slit must interact with photon, so isn't sensor reason why patterns on screen change?
So what is exactly weird in this experiment?

Many popsci presentations really grossly misrepresent “the” double slit experiment. There are at least three different types of “double slit experiment” spanning almost two centuries and showing different weirdnesses.
First, there’s the original double slit done by Thomas Young, in which we shine coherent light at a double slit and observe an interference pattern. That shows that light is a wave, and there’s nothing surprising about the appearance of a pattern or its disappearance when one of the slits is blocked.
Second, we can do the same thing with a single-photon source. The weird thing here is that we get single dots on the screen (how can a wave do that?) and even weirder, if both slits are open and we run the experiment long enough to get a bunch of dots, they clump together to form an interference pattern even though they’re coming through one at a time (so you’d think each one has to go through one slit or the other). But there’s nothing especially surprising about the pattern disappearing if we have a detector at one slit or the other, for the reason you say: the photon has to interact with it.
Third, we can do this with electrons or other regular particles. Now there’s nothing weird about getting a dot for each electron, for about the same reason that bullets make holes in a paper target, but it is very weird that the dots form an interference pattern if both slits are open.

 

[Nugatory]

How we observe photon?

We don’t. All we observe is the dot on the photographic film screen where the photon landed and was absorbed.

As an aside, any description of “the” double slit experiment that does not make this clear (which will be probably 90% of the online pop-sci video junk you’ve been wasting your time on) can reasonably be ignored.

 

[gen x]

There are at least three different types
Second, we can do the same thing with a single-photon source. The weird thing here is that we get single dots on the screen (how can a wave do that?) and even weirder, if both slits are open and we run the experiment long enough to get a bunch of dots, they clump together to form an interference pattern even though they’re coming through one at a time (so you’d think each one has to go through one slit or the other). But there’s nothing especially surprising about the pattern disappearing if we have a detector at one slit or the other, for the reason you say: the photon has to interact with it.

How we know that we fire single photon one by one? How this is even possible?

 

[Dale]

Third, we can do this with electrons or other regular particles. Now there’s nothing weird about getting a dot for each electron, for about the same reason that bullets make holes in a paper target, but it is very weird that the dots form an interference pattern if both slits are open

To me, this is the weird version. It shows that matter is a wave.

 

[Matterwave]

How we observe photon?

You get dots in the detector screen at the far end. There are no sensors in the slits.

 

[gen x]

To me, this is the weird version. It shows that matter is a wave.

is electron matter? I dont think matter can be around nucleus as it does.
I dont know what electron is, but not act as matter/bullet

 

[AlexB23]

You get dots in the detector screen at the far end. There are no sensors in the slits.

It is a shame that popular science videos and books have depicted sensors inside of the holes. The Dr. Quantum Double Slit Experiment animated short film that I watched when I was younger depicted cameras near the holes.

 

[Dale]

is electron matter?

Yes.

I dont know what electron is, but not act as matter

I don’t think that you will find any support for that claim in the professional scientific literature.

 

[gen x]

Yes.

How we prove experimentally that electron has mass?

 

[PeterDonis]

is electron matter? I dont think matter can be around nucleus as it does.
I dont know what electron is, but not act as matter/bullet

I don't know where you are getting any of this from.

"Matter" is just a word; it can mean lots of different things. But its most common meaning in the actual scientific literature is "things that have nonzero invariant mass", by contrast with "radiation", which means "things that have zero invariant mass". By that definition, electrons are matter.

As for electrons acting like bullets, sure they can: you can fire them from a cathode ray tube in a straight line at a screen and see the impacfs. That's how old televisions with picture tubes worked.

 

[Matterwave]

It is a shame that popular science videos and books have depicted sensors inside of the holes. The Dr. Quantum Double Slit Experiment animated short film that I watched when I was younger depicted cameras near the holes.

You might be remembering a version of the experiment where you do try to detect which slit the electron went through so you have which-path information. You find that in that scenario, you get two single-slit results back.

But this is a different experiment than the "standard" double slit experiment. Which is why I asked for clarification.

 

[AlexB23]

You might be remembering a version of the experiment where you do try to detect which slit the electron went through so you have which-path information. You find that in that scenario, you get two single-slit results back.

But this is a different experiment than the "standard" double slit experiment. Which is why I asked for clarification.

I did not know that there were multiple versions. And yeah, I am unsure which version OP is discussing.

 

[PeterDonis]

How we prove experimentally that electron has mass?

J. J. Thomson first showed this in experiments with cathode ray tubes in 1897. With the technology of the time, he was not able to get a direct result for the mass alone, but he showed that electrrons have a finite charge to mass ratio and estimated what it was.

In 1927, when Millikan did his oil drop experiment to determine the electron charge, one could then combine that with Thomson's results to estimate the electron mass.

Since then, of course, experimental techniques have gotten much more refined and have obtained much more accurate values for the electron mass.

Even at the High School level, the information I just gave is not hard to find. I was told about it in my high school chemistry class.

 

[Dale]

How we prove experimentally that electron has mass?

@PeterDonis mentioned the original JJ Thomson cathode ray experiment from the late 1800’s. More modern experiments would use Penning traps.

 

[gen x]

Even at the High School level, the information I just gave is not hard to find. I was told about it in my high school chemistry class.

Yes I remember that, but we also learned in school that electron orbit around nucleus in circle but that is not correct.
I knew that we learned in school that electron has mass, but what is electron?

 

[PeterDonis]

we also learned in school that electron orbit around nucleus in circle

Nobody told me that in school. But yes, it's true that not everything you get told in school is correct.

However, it's easy to check such things nowadays. There's plenty of information available online about the experiments I mentioned.

I knew that we learned in school that electron has mass, but what is electron?

Our best current answer is that it's a quantum field.

 

[Dale]

we learned in school that electron has mass

Then why would you make a claim that it isn't matter?

 

[gen x]

Then why would you make a claim that it isn't matter?

just said that donit act like classic matter.
We are talking about something the we dont know what it is..

 

[FactChecker]

How we know that we fire single photon one by one? How this is even possible?

You just have to reduce the emission rate low enough that they are only observed occasionally, one at a time.

 

[Dale]

We are talking about something the we dont know what it is..

What has that got to do with your claim of electrons not acting like matter? In any sense that we know what matter is we know what an electron is. In any sense that we don't know what an electron is, we also don't know what matter is. Electrons act just like matter.

You should read the Wikipedia entry on Matter. https://en.wikipedia.org/wiki/Matter It goes over several definitions, only one of which doesn't include electrons.

Your argument here is indefensible. If you are going to continue to claim that electrons don’t act like matter then please provide a reference to the peer reviewed scientific literature that supports the claim.

 

[Nugatory]

How we know that we fire single photon one by one? How this is even possible?

We know that we’re getting single photons one by one when the dots indicating that a photon has landed on the screen appear one at a time, or our array of photomultiplier tubes triggers one at a time, or the equivalent for whatever other equipment we’re using.

Or in most experiments we know up front that we’ll be getting photons one at a time because we’ve included a single-photon source in our experimental setup. Google will tell you a lot about how these work.

 

[PeterDonis]

We know that we’re getting single photons one by one when the dots indicating that a photon has landed on the screen appear one at a time, or our array of photomultiplier tubes triggers one at a time, or the equivalent for whatever other equipment we’re using.

Yes, but note that this is not necessarily the same as...

Or in most experiments we know up front that we’ll be getting photons one at a time because we’ve included a single-photon source in our experimental setup. Google will tell you a lot about how these work.

Actually this isn't true for "most" experiments--certainly not for most double slit experiments. Single photon sources--sources that emit Fock states--are hard to set up and control.

As far as the photon impacts are concerned, although for, e.g., a double slit experiment the interference pattern on the screen will be the same for different kinds of photon sources, other things will not be. For example, if the photon source is a laser, or even an ordinary incandescent bulb, the timing of the arrivals of the individual photon impacts on the screen will be random (in more technical language, it will follow a Poisson distribution).

But if the photon source emits Fock states, the individual impacts will occur with the same time interval (to a good approximation) between each, i.e., the timing will not be random. (This is called "antibunching" in the literature.)

There are still other kinds of sources that can produce the opposite effect--the impacts tend to occur in clumps (called "bunching" in the literature), i.e., when one impact occurs, the probability of another one in a very short time is increased (where it is decreased in antibunching, and doesn't change at all for a Poisson distribution).