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B Experiment to measure EM waves

  1. Jul 23, 2017 #1
    Okay, let me prelude this by saying I only have an -EXTREMELY- limited understanding of classical physics, and zero knowledge of quantum mechanics. This is really just my asking a few questions in regards to an idea I had for an experiment, and what would be a good and accurate way to scientifically measure it. If this is something that requires an advanced degree in QFT, please feel free to ignore this post/move it to the trash bin.

    So according to Maxwell, an oscillating electric charge set at a specific frequency generates EM/light waves. The strength of the induced field is proportional to the rate of change of the inducing field.

    Now the electric & magnetic fields 'regenerate' each other at a constant speed - the speed of light - so energy conservation is maintained. The frequency can change, but the speed of propagation never changes.

    [QUESTIONS] - 1 and 2 are not related to the experiment.
    1: Can this process be reversed? Could you somehow translate an EM wave back into an electron, or is this some string theory level crap?

    2: Can other wave types such as gravity or sound also be reversed into a corresponding particle?

    3: Can different charges besides the electric charge be used to generate any kind of field (positive/neutral), and if so what would that fields properties be?

    My objective is doing a simple little experiment in seeing what other methods exist in creating waves and measuring them. The problem lies in the fact that I'm unsure what kind of apparatus you would need to measure and set wave frequency, charge, etc... I also had a neat little idea wherein instead of somehow magically charging an object with electrons or protons I could just use cations and anions in some kind of liquid held in a test tube or something, to see if I could create a similar process, making this kind of a chemistry/physics combo. Maybe I'd use the negatively charged tube as my control group or something.

    So I'd appreciate any responses or input to my ideas here.. are they complete garbage, not doable in a home lab setting, or is my thinking way off? Basically the tl;dr is I'd like to know what (if any) devices I'd need to set this up. Thanks in advance!
  2. jcsd
  3. Jul 23, 2017 #2


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    It's the other way around, the frequency never change (at least up to linear interaction in the matter) but the speed of propagation changes depending on the refractive index.
    Search for the so-called Pair Production. This process needs EM wave with photon energy at least 1.02 MeV (i.e. gamma ray) to produce electron and positron pair.
  4. Jul 23, 2017 #3


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    It sounds to me like you are looking to experiment with radio. You certainly can build one yourself.
  5. Jul 23, 2017 #4
    Unfortunately, you seem to have quite a few misunderstandings about particles, waves, and electromagnetism in general. I will point out however, that creating EM waves from moving charges and the converse, moving charges using EM waves, is the basic premise of radio. Antenna theory would go into great detail on this matter.
  6. Jul 24, 2017 #5


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    No, not really. You cannot create a single electron from EM waves. That would be a violation of conservation of charge. Note that you aren't turning an electron into an EM wave. You are using energy to accelerate the electron and it is this energy that is being transformed into the EM wave, not the electron. You can certainly reverse this process and turn the EM wave back into another form of energy. That's what antennas and radio receivers do.

    The electromagnetic interaction (or EM force) is the only one that contains two charges with relatively simple rules for its interactions. Newtonian gravitation has a single "charge" (everything attracts) and in GR it isn't even a force. The strong and weak forces have some very complicated interactions that aren't entirely understood and aren't always analogous to electromagnetism. You can find plenty of details on these interactions on wikipedia and plenty of other places on the web.

    There are plenty of suitable RF transmitters and receivers that would work fine if you want to study EM waves. As for other waves, unless they're the waves in your bathtub or home pool, you're probably out of luck. It took billions of dollars to detect the first gravitational waves, so that's kind of out of the question, as is any investigation into the other fundamental forces.
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