Individual photons or electrons on a screen?

[johnthekid]

Are those dots actual particles of photons or electrons? I personally think those are not actual photon or electron individuals because I always thought photons and electrons are subatomic.

 

[Nugatory]

We can’t say for these exact images because we don’t know where they came from - they may be real photos or they may be simulation output. But they could be real, there are techniques sensitive enough to detect the impact of a single subatomic particle and amplify it into a visible dot on a screen or piece of photographic film.

 

[johnthekid]

We can’t say for these exact images because we don’t know where they came from - they may be real photos or they may be simulation output. But they could be real, there are techniques sensitive enough to detect the impact of a single subatomic particle and amplify it into a visible dot on a screen or piece of photographic film.

I almost give up physics everytime I saw something like this experiment. I believe the individual dots on the screen represent the interactions between electrons or photons with the atoms on the screen, but not really demonstrating that we finally observe each individual electrons or photons on a screem.

 

[PeroK]

I almost give up physics everytime I saw something like this experiment. I believe the individual dots on the screen represent the interactions between electrons or photons with the atoms on the screen, but not really demonstrating that we finally observe each individual electrons or photons on a screem.

What you need is a Photo(n)multiplier:

https://en.wikipedia.org/wiki/Photomultiplier_tube

 

[johnthekid]

What you need is a Photo(n)multiplier:

https://en.wikipedia.org/wiki/Photomultiplier_tube

Thanks, just watched a clip of a demo of how photomultiplier tubes detect photons

...and it doesn't show the individual photon particles like the double slit experiments. Instead, it shows peaks when it detect photons. Is it possible that the dots on the screen are just the grainy surface of the screen absorbing photons or electrons one by one and as the time goes the screen surface absorbs more photons or electrons?

 

[PeroK]

Thanks, just watched a clip of a demo of how photomultiplier tubes detect photons

...and it doesn't show the individual photon particles like the double slit experiments. Instead, it shows peaks when it detect photons. Is it possible that the dots on the screen are just the grainy surface of the screen absorbing photons or electrons one by one and as the time goes the screen surface absorbs more photons or electrons?

I'm not an experimentalist. Hopefully, someone else on here can give you a satisfactory answer. In the meantime, you could do your own reaseach:

https://www.rp-photonics.com/single_photon_detectors.html

 

[sophiecentaur]

What you need is a Photo(n)multiplier:

Modern sensor arrays can register individual photons with fairly high efficiency so the pattern for low intensity beams can be regarded as due to the effect of individual photons. Astrophotography can work on very low signal levels. Individual electrons of appropriate energy can register as 'dots' too. Of course, there can be random noise effects as well so many experiments use long time intervals to increase signal to noise ratio.

 

[johnthekid]

due to the effect of individual photons

Individual electrons of appropriate energy can register as 'dots' too

Therefore, the dots are just effects of the interaction between the photons or electrons with the atoms of the screen or did we finally observed individual subatomic particles?

 

[sophiecentaur]

did we finally observed

It depends on what you mean by "observe". Most of Science 'observations' involve only our direct observation of a reading on an instrument or a projected image of a result. You may see and feel a stone falling on your foot but the distance it fell and how long that took (which is the Physics of it all) is presented to us second hand by a meter display.

I don't think there is anything "finally" about this as we have been detecting individual electrons and photons for many years, It's just that, these days, we carry the instruments about in our pockets or keep them in a lab. Think about the Large Hadron Collider at CERN. With a lot of fancy equipment we can show the presence of exotic particles, never before 'seen' but we don't actually see them. In no way does that invalidate the results. It's just that the results are much more certain than they used to be with crude equipment.

 

[sophiecentaur]

it doesn't show the individual photon particles like the double slit experiments. Instead, it shows peaks when it detect photons.

Yes. That's the point. It's like any other amplifier which can produce an image (visual or aural etc.) which is more suited to our sensory needs in our front room with the lights on and the washing machine running (and instantly).

 

[johnthekid]

I don't think there is anything "finally" about this as we have been detecting individual electrons and photons for many years, It's just that, these days, we carry the instruments about in our pockets or keep them in a lab.

Do you mean our cell phones or laptops can detect an individual electron and photon?

 

[johnthekid]

Yes. That's the point. It's like any other amplifier which can produce an image (visual or aural etc.) which is more suited to our sensory needs in our front room with the lights on and the washing machine running (and instantly).

So, seeing dots on a screen is not necessary.

 

[DaveC426913]

If you're interested in seeing individual atomic particles with the naked eye, this may interest you.

https://www.newscientist.com/articl...ible-to-the-naked-eye-in-this-stunning-photo/

won the 2018 Engineering and Physical Sciences Research Council science photography competition.

The distance between those two electrodes is 2mm:

 

[sophiecentaur]

So, seeing dots on a screen is not necessary.

If you rely on "seeing is believing' then there's no way you will ever appreciate the realities of the Universe. We will only ever 'see' a tiny portion of the mechanism of our world. We (the general public) are quite happy to discuss and be aware of highly esoteric aspects of our Universe so why would we want this particular bit to rely on visual evidence? Our education is largely based on second hand information and we have to accept that.

 

[johnthekid]

If you rely on "seeing is believing' then there's no way you will ever appreciate the realities of the Universe. We will only ever 'see' a tiny portion of the mechanism of our world. We (the general public) are quite happy to discuss and be aware of highly esoteric aspects of our Universe so why would we want this particular bit to rely on visual evidence? Our education is largely based on second hand information and we have to accept that.

Let's continue on this topic next time. In the study below, at page 4 the two dimensional position sensitive electron counting system has the fluorescent screen or phosphor screen located before the photocathode, microchannel plate and position sensitive detector. In Hamamatsu PIAS or photon counting image acquisition system, the configuration is photocathode, microchannel, fluorescent screen and lastly the position sensitive detector. What is the function of fluorescent screen in the electron counting system? Should I create a new thread?

 

[sophiecentaur]

So, seeing dots on a screen is not necessary.

I responded to this post of yours and clearly didn't get your point. What was your point, in fat?
That aged paper in your attachment about the two slits experiment seems uncontroversial to me and fits in with all my comments above.

 

[johnthekid]

I responded to this post of yours and clearly didn't get your point. What was your point, in fat?
That aged paper in your attachment about the two slits experiment seems uncontroversial to me and fits in with all my comments above.

Sorry, I was very confused as I am still learning about the mechanism behind those experiments. Let's end this topic for now and continue next time.

 

[sophiecentaur]

Are those dots actual particles of photons or electrons?

To revisit the OP. "those dots' cannot be the particles (either type) from the source. To be accurate, we must say that those green dots are the results of interaction between the particle and the substance on the screen. They are 'second hand' information. The only particles that we can see directly are ones which strike our retina -they would nave to be photons, reflected from the screen or the photons generated inside a photomultiplier or other detector.

It would not be easy (impossible, I think) to see those interference patterns directly because the eye would need to be placed just where the screen is and what would be the pattern on the cells of your retina? Very confusing and where would your brain tell you that the image is? What you would see would be the two slits at the source (far enough away to focus on) with some fringes on either side of them. Your eye lens would insist on seeing the slits and not the variation of brightness (those projected fringes) across your lens. And the fringe pattern varies with distance from the source! Oh boy.