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Thread: Is light radiated by positive particles left handed?

  1. #1 Is light radiated by positive particles left handed? 
    Time Lord
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    I've been reading more about EM radiation, and apparently most radiowaves follow a "right hand rule" which means that if you're standing behind a beam of EM radiation, then at any point where the magnetic field is pointing up, the electric field is pointing to the right.

    Does the opposite charge of a positron mean that when it radiates a beam of EM radiation that the beam has its electric field pointing to the left instead?

    What would that change about the way light interacts with objects? Anything? Would some reflective objects transmit it instead of reflecting it? I'm thinking that electrons would be pulled instead of pushed.... but that probably wouldn't change the way they move up or down in their orbitals would it?


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  3. #2 Re: Is light radiated by positive particles left handed? 
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    Quote Originally Posted by kojax
    I've been reading more about EM radiation, and apparently most radiowaves follow a "right hand rule" which means that if you're standing behind a beam of EM radiation, then at any point where the magnetic field is pointing up, the electric field is pointing to the right.

    Does the opposite charge of a positron mean that when it radiates a beam of EM radiation that the beam has its electric field pointing to the left instead?

    What would that change about the way light interacts with objects? Anything? Would some reflective objects transmit it instead of reflecting it? I'm thinking that electrons would be pulled instead of pushed.... but that probably wouldn't change the way they move up or down in their orbitals would it?
    That is not what the right hand rule means.

    The right hand rule applies to the vector cross product, and is a mathematical rule, not a physical rule.

    The rest of your questions don't really make sense and they make assujmptions that are just plain wrong. You need to read a good book on electromagnetic theory. See several recommendations in other threads related to questions that you have asked there.


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  4. #3 Re: Is light radiated by positive particles left handed? 
    Time Lord
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    Quote Originally Posted by DrRocket
    Quote Originally Posted by kojax
    I've been reading more about EM radiation, and apparently most radiowaves follow a "right hand rule" which means that if you're standing behind a beam of EM radiation, then at any point where the magnetic field is pointing up, the electric field is pointing to the right.

    Does the opposite charge of a positron mean that when it radiates a beam of EM radiation that the beam has its electric field pointing to the left instead?

    What would that change about the way light interacts with objects? Anything? Would some reflective objects transmit it instead of reflecting it? I'm thinking that electrons would be pulled instead of pushed.... but that probably wouldn't change the way they move up or down in their orbitals would it?
    That is not what the right hand rule means.

    The right hand rule applies to the vector cross product, and is a mathematical rule, not a physical rule.
    Ok, my understanding of the right hand rule was at least incomplete, but I thought that what I said followed from the mathematical rule. If X is the electric field vector and Y is the magnetic field vector, then the direction of motion should be Z.

    http://upload.wikimedia.org/wikipedi...handedness.svg

    Perhaps I should have asked the question differently, though. I'm thinking of another thread. http://www.thescienceforum.com/viewt...26585&start=15 I was thinking that if a radio wave emitted by moving electrons were to encounter a free electron in space, then it would tend to push the electron away from the source of the radio wave. It would be just like in a rail gun. The electric field is pointing left when the magnetic field is pointing down (and the electric field is pointing right when the magnetic field is pointing up).

    However, if moving positrons were the source of the radio wave, then I would expect that it would tend to pull the free electron back toward the source. Presumably, the electric field would be backwards from where it points when electrons are the emitter.





    The rest of your questions don't really make sense and they make assujmptions that are just plain wrong. You need to read a good book on electromagnetic theory. See several recommendations in other threads related to questions that you have asked there.
    I've scanned back through several of them. The only book recommendation I see in your posts is "Goldstein's Classical Mechanics." The title makes it sound like it wouldn't have what I'm after, but I will certainly look for it.

    This has actually been a major problem for me. I can't seem to find any books that clearly describe what's happening in terms that I can make a diagram for myself out of. The few I use (such as my own physics text book) like to use flowery analogies rather than just say what they mean. It's very frustrating. I'd actually rather just have everything expressed as vectors and do the math, as long as the descriptions are complete. The trouble is my textbook only covers the basics of EM theory, just a few pages, and everything else I can find is either too basic, or assumes I already know everything about EM.
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  5. #4  
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    By the way ... em-fields move electrons in an antenna up and down. If the
    antenna absorbs energy, then it is pushed backwards.
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  6. #5 Re: Is light radiated by positive particles left handed? 
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    Quote Originally Posted by kojax
    Quote Originally Posted by DrRocket
    Quote Originally Posted by kojax
    I've been reading more about EM radiation, and apparently most radiowaves follow a "right hand rule" which means that if you're standing behind a beam of EM radiation, then at any point where the magnetic field is pointing up, the electric field is pointing to the right.

    Does the opposite charge of a positron mean that when it radiates a beam of EM radiation that the beam has its electric field pointing to the left instead?

    What would that change about the way light interacts with objects? Anything? Would some reflective objects transmit it instead of reflecting it? I'm thinking that electrons would be pulled instead of pushed.... but that probably wouldn't change the way they move up or down in their orbitals would it?
    That is not what the right hand rule means.

    The right hand rule applies to the vector cross product, and is a mathematical rule, not a physical rule.
    Ok, my understanding of the right hand rule was at least incomplete, but I thought that what I said followed from the mathematical rule. If X is the electric field vector and Y is the magnetic field vector, then the direction of motion should be Z.

    http://upload.wikimedia.org/wikipedi...handedness.svg

    Perhaps I should have asked the question differently, though. I'm thinking of another thread. http://www.thescienceforum.com/viewt...26585&start=15 I was thinking that if a radio wave emitted by moving electrons were to encounter a free electron in space, then it would tend to push the electron away from the source of the radio wave. It would be just like in a rail gun. The electric field is pointing left when the magnetic field is pointing down (and the electric field is pointing right when the magnetic field is pointing up).

    However, if moving positrons were the source of the radio wave, then I would expect that it would tend to pull the free electron back toward the source. Presumably, the electric field would be backwards from where it points when electrons are the emitter.





    The rest of your questions don't really make sense and they make assujmptions that are just plain wrong. You need to read a good book on electromagnetic theory. See several recommendations in other threads related to questions that you have asked there.
    I've scanned back through several of them. The only book recommendation I see in your posts is "Goldstein's Classical Mechanics." The title makes it sound like it wouldn't have what I'm after, but I will certainly look for it.

    This has actually been a major problem for me. I can't seem to find any books that clearly describe what's happening in terms that I can make a diagram for myself out of. The few I use (such as my own physics text book) like to use flowery analogies rather than just say what they mean. It's very frustrating. I'd actually rather just have everything expressed as vectors and do the math, as long as the descriptions are complete. The trouble is my textbook only covers the basics of EM theory, just a few pages, and everything else I can find is either too basic, or assumes I already know everything about EM.
    This is too screwed up to respond to in detail.

    Try reading Marion's Classical Electromagnetic Radiation or Jackson's Classical Electrodynamics. The former is an undergraduate text the latter is the standard graduate text. Another good undergraduate text is Introduction to Electrodynamics by Griffiths.
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  7. #6  
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    I've been assuming this picture is correct :

    http://en.wikipedia.org/wiki/File:On...magnetique.svg

    ...And I guess it may not be. I think the question I should ask is: is it possible for the electric field to point to the right while the magnetic field is pointing upwards instead of pointing left as it does in the picture, or be a quarter way out of phase, or are the two always in sync?


    Your remark, though scathing in nature, ... has motivated me to actually do the math. (I realize now that I have to use vector mathematics if I ever want to be a proper physicist even though I don't like it very much.) I'm starting to see the flaws in my reasoning more clearly. Using the Lorentz force equation:



    I see now where my mistake is (at least part of it). If a very strong, low frequency radio wave were to act on a stationary electron in free space, then ..... as soon as the electric field induces the electron to move right or left, the magnetic field will begin to push it toward or away from us. However, once the fields switch direction, the electron will keep moving in that same right or left direction it was going before until the electric field brings it to a stop in the right/left direction, and all the while the magnetic field will be bringing it to a stop in the forward/backward direction.

    So... there is no net acceleration created when the wave does a complete cycle, at least not when it acts on a stationary electron, anyway.
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  8. #7  
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    Quote Originally Posted by kojax
    I've been assuming this picture is correct :

    http://en.wikipedia.org/wiki/File:On...magnetique.svg

    ...And I guess it may not be. I think the question I should ask is: is it possible for the electric field to point to the right while the magnetic field is pointing upwards instead of pointing left as it does in the picture, or be a quarter way out of phase, or are the two always in sync?


    Your remark, though scathing in nature, ... has motivated me to actually do the math. (I realize now that I have to use vector mathematics if I ever want to be a proper physicist even though I don't like it very much.) I'm starting to see the flaws in my reasoning more clearly. Using the Lorentz force equation:



    I see now where my mistake is (at least part of it). If a very strong, low frequency radio wave were to act on a stationary electron in free space, then ..... as soon as the electric field induces the electron to move right or left, the magnetic field will begin to push it toward or away from us. However, once the fields switch direction, the electron will keep moving in that same right or left direction it was going before until the electric field brings it to a stop in the right/left direction, and all the while the magnetic field will be bringing it to a stop in the forward/backward direction.

    So... there is no net acceleration created when the wave does a complete cycle, at least not when it acts on a stationary electron, anyway.
    Yep, if you are going to be a proper physicist, you will have to do some vector analysis. In fact you will have to rather a lot of it and become quite proficient. In fact that is just the tip of the iceberg. You will have to become fmiliar with ome much more sophisticated techniques.

    Now, look a little closer. The magnetic field acts perpendicularly to the velocity vector. That is why a charged particle moving in a fixed magnetic field takes a helical path. Note also that since the magnetic component of the force is perpendicular to the velocity vector, which is tangent to the trajectory, that the magnetic component does no work.

    In your readings you might want to consider the section on the Poynting vector.
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