| MadSci Network: Physics |
Hi Stewart,
Unfortunately you're starting with an incorrect description of the double-slit experiment. There is not one "real" electron interfering with one "virtual" electron; you have one electron wave which passes through both slits, interferes with itself, and behaves like a particle only when it hits the detecting screen. (Perhaps you would say that both slit 1 and slit 2 transmit virtual electrons, which become real when they hit the screen, but this is NOT the most common usage of the word "virtual".)
This is the concept of "wave-particle duality". A single electron, (or proton, photon, whatever) can manifest both wave-like behaviors and particle-like behaviors at the same time. Examples of wave-like behaviors include: diffraction, interference, boundary conditions. Examples of particle-like behavior include: the fact that the electron hits a single point on the detector; quantization of charge. The double-slit experiment is cool because it demonstrates both behaviors (wave interference, and particle-like interaction with the detection screen) very un-ambiguously.
To really understand the wave-particle duality (it's really not so mysterious!) you need to know the basic math of quantum mechanics - an undergrad-level textbook like "Quantum physics of atoms, molecules etc ..." by Eisberg and Resnick is a good place to start, or for a better armchair reading try "Quantum Reality" by Nick Herbert. Also, take a look at this web page.
Hope this helps!
-Ben
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