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Name: nick
Status: student
Age: 14
Location: N/A
Country: N/A
Date: 2000-2001


Question:
In Thomas Young's double slit experiment:

How is it possible that an electron takes multiple paths through the slits?

Dosen't this violate the laws governing constant mass?


Replies:
The electron does not take multiple paths through the slits. Interference fringes result from the mere fact that the different paths the electron *could* take (from the source, through the slits, to a particular spot) have different lengths. Very strange -- spooky, even -- but very well established by experiment, and mimicking precisely the pattern one would expect if a wave spreading out from the source encountered those slits.

Tim Mooney


Well, it's somewhat misleading to say that the electron "takes multiple paths through the slits." It would be more accurate to say that it acts as if it goes through both slits at once. What actually happens is that an electron fired at the barrier either makes it through the slits and to the screen on the other side, or it doesn't. If it makes it through, it strikes the screen somewhere. You can't predict exactly where it will strike the screen. When it strikes the screen somewhere, you can't know for sure which slit it passed through to get there.

When enough electrons land on the screen, their impacts form a diffraction pattern as if they are waves, not particles. Waves, as you know, can pass through two slits at once, forming two wavefronts that can interfere with each other. How can individual, non-interacting electrons form a diffraction pattern unless each one somehow passes through both slits? Oddly, even though electrons are detected at only one spot, they act in a way as if they are waves. Otherwise, how would they form a diffraction pattern?

Sounds weird, but it's true. Quantum mechanics is like that.

Richard E. Barrans Jr., Ph.D.
Assistant Director
PG Research Foundation, Darien, Illinois



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