How Do Electrons Overcome Wave-Particle Duality in CRT Monitors?

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Discussion Overview

The discussion centers on the behavior of electrons in cathode ray tube (CRT) monitors, specifically addressing how electrons can be directed to specific locations on the screen despite their wave-particle duality. Participants explore the implications of quantum mechanics on the functioning of CRTs, including the roles of electron diffraction and interference.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • Some participants suggest that the electron gun in CRTs fires many electrons, resulting in an average effect that aligns with classical trajectories, despite the wave nature of electrons.
  • Others argue that the wave-like properties of electrons are not suppressed, and the larger target area of pixels allows for accurate direction of electrons.
  • Concerns are raised about the probability of electrons hitting unintended pixels, with some noting that such occurrences are more likely due to electronic inaccuracies rather than quantum effects.
  • Participants reference the double slit experiment to illustrate that electrons can diffract, leading to uncertainty in their exact landing position on the screen.
  • Some discuss historical issues with color CRTs, mentioning the need for precise adjustments of shadow masks and the impact of wave interference on image quality.
  • There is a mention of the relationship between pixel spacing and phosphor dot arrangements, with some asserting that the electron spot covers multiple pixels.
  • Discussions also touch on the implications of wave interference in the context of television broadcasts and the effects of patterns on presenters' clothing.
  • Questions arise regarding the wavelength of electrons and their energy levels in CRTs, with references to de Broglie wavelength calculations.

Areas of Agreement / Disagreement

Participants express multiple competing views regarding the influence of wave-particle duality on electron behavior in CRTs. The discussion remains unresolved, with differing opinions on the significance of quantum effects versus classical explanations.

Contextual Notes

Limitations include assumptions about the accuracy of electron targeting, the dependence on specific definitions of wave-particle duality, and unresolved mathematical considerations regarding electron diffraction.

sawer
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How do CRTs work well and electrons can be sent to exact location on screen in CRT monitors if electrons can behave like wave?

Is there something in old TVs (for example measurement device) along the road that electron travels to avoid behave like wave?
 
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The electron gun in a TV set fires very many electrons so what you see on the screen is the average from many quantum-level events.
The statistics work out so that the average is the classical trajectory.

The wave nature of electrons is statistical - it is not a wave like you see on water - what gets detected is always a particle in that all the energy arrives in one go at a specific location.

This means that some electrons from the gun do go astray - it's just that the probability of getting close to the target is so high that the target glows much brighter that you don't see the misses.

Please view:
http://www.vega.org.uk/video/subseries/8
 
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There is nothing that suppresses the wave-like properties of electrons. The key is that the target area, a pixel on the screen, is much, MUCH larger than an electron and it is relatively easy to direct their path with essentially 100% accuracy.
 
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Hmmm...

1-) But there is always a chance to find it on another pixel right?

2-) In double slit experiment, we can observe electrons can diffract and we can't be sure where to to find it on screen. This is also true for without double slit case right? I mean if we fire an electron and even there is no double slit vs. between gun and screen, there is a probability to find electron anywhere on screen. Right?

Thanks for the answers.
 
sawer said:
Hmmm...

1-) But there is always a chance to find it on another pixel right?

2-) In double slit experiment, we can observe electrons can diffract and we can't be sure where to to find it on screen. This is also true for without double slit case right? I mean if we fire an electron and even there is no double slit vs. between gun and screen, there is a probability to find electron anywhere on screen. Right?

Thanks for the answers.
That was a real problem with colour TV CRT's. They had a mask with tightly spaced holes just behind the phosphorous. You had to adjust it as best you could, involving lots of compromises...
 
sawer said:
1-) But there is always a chance to find it on another pixel right?

The chances of the electron being found in the next pixel over are far more likely to be because of a malfunction or inaccuracy in the electronics that target the electrons than because of quantum effects.

sawer said:
2-) In double slit experiment, we can observe electrons can diffract and we can't be sure where to to find it on screen. This is also true for without double slit case right? I mean if we fire an electron and even there is no double slit vs. between gun and screen, there is a probability to find electron anywhere on screen. Right?

Sure, but the chances are absolutely miniscule. They're so small that you don't even need to take the diffraction of electrons into account when designing the TV.
 
Svein said:
That was a real problem with colour TV CRT's. They had a mask with tightly spaced holes just behind the phosphorous. You had to adjust it as best you could, involving lots of compromises...

I doubt any of these TV's were experiencing problems because of electron diffraction.
 
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sawer said:
How do CRTs work well and electrons can be sent to exact location on screen in CRT monitors if electrons can behave like wave?

How can baseball pitchers deliver the ball to an exact location in the cater's glove if baseballs are waves?
 
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Svein said:
That was a real problem with colour TV CRT's. They had a mask with tightly spaced holes just behind the phosphorous. You had to adjust it as best you could, involving lots of compromises...
That wasn't a problem of QM. The dimensions of an electron gun (and the whole CRT) take matters way out of the region of diffraction. Any beam spreading and also the resulting lack of colour purity is down to the very tight margins for a shadow mask (and the subsequent improvements) and the fields which deflect the electron beam. Electrons can be treated as 'simple' charged particles when you're designing electron optics in this context, I'm sure.
Pixels and the spacing of the phosphor dots are not necessarily related. As far as I know, the 'spot' covers several pixels - there are only 700 pixels across the screen and far more colour phosphor triads.
 
  • #10
Drakkith said:
I doubt any of these TV's were experiencing problems because of electron diffraction.
Possibly not, but wave interference was a real problem. TV presenters were not allowed to wear clothes with fine patterns...
 
  • #11
sophiecentaur said:
Pixels and the spacing of the phosphor dots are not necessarily related. As far as I know, the 'spot' covers several pixels - there are only 700 pixels across the screen and far more colour phosphor triads.
deltagun_big.jpg

https://en.wikipedia.org/wiki/Cathode_ray_tube
 
  • #12
Svein said:
Possibly not, but wave interference was a real problem. TV presenters were not allowed to wear clothes with fine patterns...
It was due to limitations of PAL and NTSC as well as interlacing jitter
 
  • #13
Svein said:
Possibly not, but wave interference was a real problem. TV presenters were not allowed to wear clothes with fine patterns...
OMG. That's a bit of a wild guess; the orders of magnitude are all wrong for diffraction. :wink: It's to do with the colour coding on the signal and it's there on the drive to the tube. In PAL and NTSC, there is a 'subcarrier' at 4.43MHz (PAL), which carries the colour (chrominance) information. This subcarrier forms beats with high frequency video components. These beats are whet you see when the picture content is stripy. A 4.2 MHz grille will produce 230kHz fringes - very visible. The effect is not as visible on single sharp edges so the picture is ok if you avoid regular hf patterns.
 
  • #14
Svein said:
deltagun_big.jpg

https://en.wikipedia.org/wiki/Cathode_ray_tube
A detail that the diagram does not show is that the three beams have to come from the same virtual point in space, despite the electron guns and grids are fairly wide, so the shadow mask works onver the whole screen. (Also, the beams go through more than just one hole at a time to make the picture bright enough). The beams from the three guns have to be bent by magnetic fields to achieve this. No wonder those shadow mask tubes had to be set up every day for high quality stdio use. TGF LCDs.
 
  • #15
Svein said:
Possibly not, but wave interference was a real problem. TV presenters were not allowed to wear clothes with fine patterns...

What does wave interference mean in this context?
 
  • #16
Vanadium 50 said:
How can baseball pitchers deliver the ball to an exact location in the cater's glove if baseballs are waves?

Lots and lots of practice? :-p
 
  • #17
Drakkith said:
What does wave interference mean in this context?
The shirt problem was intermodulation, whatever he means. It happened on flat screen PAL receivers.
 
  • #18
Drakkith said:
What does wave interference mean in this context?
The holes were close enough to create an optical grid...
 
  • #19
Svein said:
The holes were close enough to create an optical grid...
What wavelength would you assign to the electrons, though?
Hint; look at this link for an idea. It shows the de Broglie Wavelength of a 100eV electron is 0.12nm and electrons in a CRT have many keV of energy.
 
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