Double slit experiment

[Brainee]

What happens when one of 2 people shoots an electron through a double slit and the other watches where it lands?

[joigus]

The second person would see the electron land somewhere on a screen and wouldn't notice anything remarkable at all. No interference, because it's just one electron.

It's been done, and that's what happens.

[swansont]

1 hour ago, joigus said:

The second person would see the electron land somewhere on a screen and wouldn't notice anything remarkable at all. No interference, because it's just one electron.

It's been done, and that's what happens.

I disagree. There is no interference pattern because it’s just one electron. But there is interference, and the electron will hit the screen only in a spot that corresponds to an interference maximum. That the electron might not land along its classical trajectory (i.e. not the m=0 location) is IMO remarkable. And yes, this experiment has been done, in showing that the interference pattern shows up after repeated single electrons passing through the double slit.

[studiot]

The double slit, for some reason, is one of the most controvertial experiments in physics.

+1 to swansont for a better, though brief answer.

 

The most compact description of what happens and our best explanation I know of is to be found in Dicke and Wittke's Introduction to Quantum Mechanics, an altogwether excellent, if a bit dated, tome.

 

I know my extract is in terms of photons, but if you read the book it does deal with electrons and other massive particles, however basic questions should be addressed in basic terms first. Light can be dealt with directly, as was done since Young's day, but quite a bit of later (eg De Broglie) theory is needed to move on to electrons.

 

Edited August 20, 2022 by studiot

[joigus]

1 hour ago, swansont said:

I disagree. There is no interference pattern because it’s just one electron. But there is interference, and the electron will hit the screen only in a spot that corresponds to an interference maximum. That the electron might not land along its classical trajectory (i.e. not the m=0 location) is IMO remarkable. And yes, this experiment has been done, in showing that the interference pattern shows up after repeated single electrons passing through the double slit.

That's what I meant. There is no interference pattern. There is interference, of course, but we wouldn't be any the wiser about it by watching just one electron. Thank you, because I think the point is important. Sometimes brevity is not your best friend.

[Brainee]

I meant if you fire many electrons.

[studiot]

12 hours ago, Brainee said:

I meant if you fire many electrons.

I'm guessing, from your questions, that you are a student just starting to learn this stuff.

Sensible questions, like the ones you have been asking, are very good so keep asking.

But you will get so much more out of the discussion the you put more into it.

Short answers like that to folks who have put in quite a bit of effort to help you will lead to them rapidly loosing interest.

[swansont]

If you fire many electrons you will see the interference pattern. The pattern goes away if you can determine that an electron went through a particular slit, but that's not the case simply because a different person observes the screen.