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B Double slit experiment question

  1. Jun 13, 2017 #1
    In the double slit experiment does the screen and the cardboard with the slits count as an observer since the electron interacted with them?
     
  2. jcsd
  3. Jun 13, 2017 #2

    Nugatory

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    Staff: Mentor

    When an electron interacts with the screen to leave a dot at some point, that's an observation of the position of the electron so you could say that the screen has observed the position of the electron at the moment it reaches the screen. Note the screen+electron system has been irreversibly changed by this interaction.

    Interaction between the barrier and the electrons as they pass through the slits may or may not provide a measurement of the position of the electron at that moment.
     
  4. Jun 13, 2017 #3
    Then why is the detector used able to cause the electron to choose which slit to go through but not the screen?
     
  5. Jun 13, 2017 #4

    Nugatory

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    The barrier and the screen are completely different objects with completely different construction. Why would we not expect them to interact differently with nearby electrons? Indeed, we've deliberately designed them to interact differently - we've designed the screen to absorb every electron that reaches it, and we've designed the barrier to interact as little as possible with the electrons passing through the slits.

    An electron detector is a device that is designed to interact irreversibly with electrons. It should not be surprising to find that a putting such a device in one of the slits produces interactions that wouldn't happen if the detector were not there.
     
    Last edited: Jun 14, 2017
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