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Thread: Question on QM basic measurements

  1. #1 Question on QM basic measurements 
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    Can you provide info on this :

    QM assigns all sorts of characteristics to the quantum particles slash waves, and electromagnetic behaviour has certain characteristics.


    Ok, but what are the basic experimentally observed data to conclude this that and the other ?



    So what was the barebone input coming out of observational experiments that lead to the formulation of the characteristics of the particles slash waves ?

    Links perhaps ? (Not on the theory but on the above)

    I understand the uncertainty principle, the ambivalent measurement issue.


    It is more on to this :


    'An electon mass is this much eV, charge is , and spin is… '


    What are the input data for this ?




    I am interpreting these 3 parameters in therms of what they mean in a gravity model i work on,
    And therefore i would like to see if i could also derive the same , starting from the barebone data of input.


    Last edited by Noa Drake; November 18th, 2013 at 05:38 PM.
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  3. #2  
    Moderator Moderator Markus Hanke's Avatar
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    What are the input data for this ?
    What do you mean by "input data" ?

    I am interpreting these 3 parameters in therms of what they mean in a gravity model i work on,
    If your question is about sources of gravity, then this is described mathematically by the energy-momentum tensor.


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  4. #3  
    Brassica oleracea Strange's Avatar
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    Quote Originally Posted by Noa Drake View Post
    'An electon mass is this much eV, charge is , and spin is… '


    What are the input data for this ?
    This is all far too vague. There are many different experimental results that lead to these values.

    For example, one of the earliest experiments on the electron was the Millikan oil drop experiment:
    The experiment entailed balancing the downward gravitational force with the upward drag and electric forces on tiny charged droplets of oil suspended between two metal electrodes. Since the density of the oil was known, the droplets' masses, and therefore their gravitational and buoyant forces, could be determined from their observed radii. Using a known electric field, Millikan and Fletcher could determine the charge on oil droplets in mechanical equilibrium. By repeating the experiment for many droplets, they confirmed that the charges were all multiples of some fundamental value, and calculated it to be 1.5924(17)×10−19 C, within 1% of the currently accepted value of 1.602176487(40)×10−19 C. They proposed that this was the charge of a single electron.
    Oil drop experiment - Wikipedia, the free encyclopedia

    Knowing the charge, you can then measure the deflection of a beam of electrons in a magnetic or electric field and calculate the mass of the electron. Other experiments will measure the spin, etc. But note that spin was first observed through its effect on the emission spectrum of atoms.
    ei incumbit probatio qui dicit, non qui negat
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  5. #4  
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    Quote Originally Posted by Noa Drake View Post
    Can you provide info on this :

    QM assigns all sorts of characteristics to the quantum particles slash waves, and electromagnetic behaviour has certain characteristics.


    Ok, but what are the basic experimentally observed data to conclude this that and the other ?



    So what was the barebone input coming out of observational experiments that lead to the formulation of the characteristics of the particles slash waves ?

    Links perhaps ? (Not on the theory but on the above)

    I understand the uncertainty principle, the ambivalent measurement issue.


    It is more on to this :


    'An electon mass is this much eV, charge is , and spin is… '


    What are the input data for this ?




    I am interpreting these 3 parameters in therms of what they mean in a gravity model i work on,
    And therefore i would like to see if i could also derive the same , starting from the barebone data of input.
    As others have said, this is a rather vaguely expressed series of questions. But if you want a guide to the history of how the idea arose that radiation energy consists of quantised amounts, rather than a continuum, you could try looking up the "Ultraviolet Catastrophe" and the Photo-Electric Effect.

    For the converse idea, that subatomic particles such as electrons behave in some respects as waves, try looking up Louis De Broglie.

    Once these two ideas had come together, the wave-particle duality of matter was pretty well in place and Quantum Mechanics took shape pretty rapidly.
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  6. #5  
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    I'll try and refrase :

    The electric and magnetic component of the EM-radiation, or the particle characteristics, the propagation along the straight line, can be measured.

    What does the measurement device do exactly ?
    How does it interact to perform these measurements ?

    What are 'the fysical tentacles' of the measurement device if you will (if their are any) ?
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  7. #6  
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    Quote Originally Posted by Noa Drake View Post
    I'll try and refrase :

    The electric and magnetic component of the EM-radiation, or the particle characteristics, the propagation along the straight line, can be measured.

    What does the measurement device do exactly ?
    How does it interact to perform these measurements ?

    What are 'the fysical tentacles' of the measurement device if you will (if their are any) ?
    The means of measuring the energy and frequency (or wavelength) of EM radiation depends on the frequency range involved.

    Energy detectors, which measure "quanta" i.e. particles, usually involve absorption of the EM energy and conversion to another form, such as electrical, that can easily be amplified and quantified. The way this is done depends on the frequency.

    For frequency and wavelength you may use some form of "resonance" detector, such as the tuning of a radio ariel, or you might use a spectrometer, which works by spreading out different frequencies spatially so the frequency can be determined by the point on a spread out energy detector where the beam impinges.

    I'm conscious that I'm still not really sure what you are asking, though, so apologies if this is not what you were after.
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  8. #7  
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    Yes that is what it is about, thank you.

    " the frequency can be determined by the point on a spread out energy detector where the beam impinges."

    Could you provide more detail about this perhaps ?
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  9. #8  
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    I found some additional info here

    Topic 7. Detecting Electromagnetic Radiation

    http://academia.hixie.ch/bath/em/home.html



    A
    nd an overview on how their sources/mechanisms of emission

    http://www.nrao.edu/index.php/learn/...omy/radiowaves
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  10. #9  
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    Quote Originally Posted by Noa Drake View Post
    I found some additional info here

    Topic 7. Detecting Electromagnetic Radiation

    http://academia.hixie.ch/bath/em/home.html



    A
    nd an overview on how their sources/mechanisms of emission

    How Radio Waves Are Produced
    Good. Are you OK with this now or do you need any further help?
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