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How do you observe the position of an electron?

  1. Aug 14, 2011 #1
    How do you "observe" the position of an electron?

    Do you use x-rays?

    If so, what happens when you hit the orbital of a given atom with x-rays? Will it just accelerate the electron(s) out of the orbital? Also, how can you then infer the position the electron had initially occupied? Do you just have detectors set around the bombarded atom? Since you know everything about your fired x-ray (intensity, wavelength etc.), you can solve for the position at impact? EDIT: You probably can't, because which detector is hit by the electron depends on the velocity and position of the electron at impact (neither of which you know). EDIT2: But if you know the temperature of the atom, then do you not know at what velocity the kicked-out electron moves? EDIT3: You only know speed but not the actually direction of motion?

    Then, when this experiment was repeated a lot of times, the probability density functions were established?
    Last edited: Aug 14, 2011
  2. jcsd
  3. Aug 14, 2011 #2


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    Re: How do you "observe" the position of an electron?

    X-ray is just one of the solutions.
    You may focus your X-ray on a very small area. So if you notice the electron kicked out - you are sure it got kicked from the focus point.

    You may also build pretty small detector to catch electrons. Actually, such detector may be not much bigger than single molecule.

    If you don't need such accuracy - watch TV (old-fashioned, CRT, not a flat one) As the electron hits the screen it flashes.
  4. Aug 14, 2011 #3
    Re: How do you "observe" the position of an electron?

    With current technology, at what resolution can we focus an xray beam (in units of a hydrogen atom diameter, say)?

    But you don't know what the velocity of the electron was. You might know speed but not velocity. Is it not like Billiard balls? Does the velocity of the electron not matter (e.g., if the xray photon [the cue] hit the electron [8-ball], does the velocity of the 8-ball not matter at impact?
    EDIT: Nevermind, you're right. You do not measure the final electron velocity or even which detector was hit - just the fact that is was kicked out, and the knowledge of which region within the orbital you beamed away.

    EDIT2: What if you did measure terminal velocity (at detection) and terminal detector position? We know xray photon velocity, speed of electron at impact (from room temperature), velocity of electron at detection, detector position that's being hit by the electron - we can solve for velocity at collision. Also, from your inference we can determine position simultaneously. Therefore, I claim that the uncertainty principle is bogus. Where is my mistake?
    Last edited: Aug 14, 2011
  5. Aug 14, 2011 #4
    Re: How do you "observe" the position of an electron?

    you know it only with a degree of error, the smaller that error for velocity the greater the error for its exact position. Also you seem to be inferring that we can predict one thing from the result another, but we cant, not with certainty.
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