Section 5.5: The Electron Double-Slit Experiment

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This animation shows double-slit experiments.  Restart.   Light (of a given wavelength) travels through two slits that are close together (close as defined relative to the wavelength of the light).  Drag the detector slowly across the light pattern to see the intensity as a function of position (position is given in mm and intensity is in arbitrary units, scaled so that the maximum intensity is 1).

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In the second animation, however, electrons are incident on a double slit and pass through to a screen as shown. Restart.  Each of the five animations gives a snapshot of the data collected at a later time period.

  1. What do you see in the animations?
  2. Do you see an interference pattern evolving?
  3. How does it compare to the interference pattern of light?
  4. Can a single electron end up anywhere on the screen or are there forbidden regions on the screen where an electron cannot land?

Electrons, as it turns out, do create an interference pattern. So even though we think of electrons as particles and when we collide them into other particles they act just as we expect particles to behave, we must, to understand this experiment, think of them as waves that interfere.