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Thick Double Slit

  1. Jan 19, 2009 #1

    A question that came up today that I do not know how to answer. We were discussing (High School) the double slit experiment and that electrons show interference patterns too. A student asked if the thickness of the double slit slide mattered. ie if the slits were a metre deep ... would this effect the pattern (my assumption is no ....)

    Thanks for any comments

  2. jcsd
  3. Jan 19, 2009 #2
    My intuition says no as well. Immagine classical waves of water traveling town two adjacent canals. Unless there is a difference in the path leingth, each wave would act as a point source when exiting the far side.
  4. Jan 19, 2009 #3
    To notice patterns you need very thin slits, if you have thick slits you wont be able to notice any change since construction destruction all occur so close together.
  5. Jan 19, 2009 #4
    Thamks atavistic ... however the student considered thick in the direction perpendicular to the screen, along the direction of motion
  6. Jan 19, 2009 #5
    SimonB, since you're the teacher, you may care to look up how to actually calculate the interference pattern (and not just the positions of the maxima). As for the students benefit, you could try demonstrating a laser pointer directed through more than one double-slit slide, or if you have less equipment, directed through one or two hairs from your (student's?) head (or parallel to the surface of small slips of paper).
  7. Jan 20, 2009 #6
    Thanks, I will of couse be doing the usual stuff.

    I have talked to the student and his reasoning is as follows.

    We had watched a video clip for electron interference. It described how the interference pattern is destroyed when the electron is observed entering one or other slit. The electron being disturbed by the observation. His reasoning was to use very long (in direction of travel) slits so the observation could be delayed ...
  8. Jan 20, 2009 #7
    Yeah, that way lies madness.. but is very interesting provided you're careful. You might want to look up the $10 quantum eraser, or the delayed choice quantum eraser. (I recommend against thinking of the observation as mechanically disturbing the system, and concentrate more on how much external information is present about the system. And of course, study classical waves in detail.)
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