Details of the double-slit experiment?

[very_curious]

Hi,

not sure if this is the right section, but I'll post this here anyway. I'm after some specific details of the famous double slit experiment with electrons:

1. How wide are the slits?
2. How far apart are the slits?
3. What is the barrier (i.e. around the slit) made of?
4. How can we test if the electrons hitting the screen are the same electrons that left the 'gun'?

Any help would be great :)

Thanks,

 

[wasia]

1. How wide are the slits?
2. How far apart are the slits?
3. What is the barrier (i.e. around the slit) made of?
4. How can we test if the electrons hitting the screen are the same electrons that left the 'gun'?

I think the abstract of the original paper answers questions 1-3:

A glass plate covered with an evaporated silver film of about 200 Angstrom thickness is irradiated by a line-shaped electron-probe in a vacuum of 10^-4 Torr. A hydrocarbon
polymerisation film of very low electrical conductivity is formed at places
subjected to high electron current density. An electrolytically deposited copper
film leaves these places free from copper. When the copper film is stripped a grating
with slits free of any material is obtained. 50 microns long and 0.3 microns wide slits with a
grating constant of 1 micron are obtained. The maximum number of slits is five.
The electron diffraction pattern obtained using these slits in an arrangement
analogous to Young's light optical interference experiment in the Fraunhofer plane
and Fresnel region shows an effect corresponding to the well-known interference
phenomena in light optics.

This was taken from Jönsson C,(1961) Zeitschrift für Physik, 161:454–474 (the paper itself is in German). Wikipedia also gives a reference to "Jönsson C (1974). Electron diffraction at multiple slits. American Journal of Physics, 4:4–11", which surely is in English.

The "shut up and calculate"-style answer to the 4th question would be that electrons are quantum particles, therefore indistinguishable! Perhaps somebody else can offer a better and more philosophical answer :)

 

[juzzy]

"How can we test if the electrons hitting the screen are the same electrons that left the 'gun'?"

The electron beam can be slowed to a rate equivalent to around 10 electrons per second, so in viewing it as a true particle it is obvious that the electron left the gun, went through one of the slits and hit the screen. The electron could not have interfered with another electron. The same way bullets from a gun could not interfere with each other. But in reality they do interfere with each other, or at least the electron somehow interferes with itself to produce the interference pattern. The idea of which electron left the gun and which one hit the screen gets a little fuzzy because we can't measure it without collapsing the wavefunction and thereby determining which one left the gun and which one hit the screen.