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Electromagnetic waves point to point propagation

  1. May 17, 2015 #1
    Is there a theoretical way to force electromagnetic waves transfere energy point to point like electricity instead omni-dirrectionally? I think it might be helpful for looseles wireless energy transfere.
     
  2. jcsd
  3. May 17, 2015 #2

    Vanadium 50

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    Like a flashlight?
     
  4. May 17, 2015 #3
    No. Waves suppose to go for any distance and walk around any obstacles without looses. They need to have some kind of an absolute diffraction. Light could propagate linearly, only.
     
  5. May 17, 2015 #4

    Vanadium 50

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    Sorry, but no.
     
  6. May 17, 2015 #5
    Use fibre optics. It walks around all kinds of stuff.
     
  7. May 18, 2015 #6
    No. Need wireless.
     
  8. May 18, 2015 #7

    davenn

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    nothing is lossless, so no, you cannot do it

    various RF antennas can be used to beam a large portion of the energy in a particular direction, but there is still lots of spreading out of the energy
    and the longer the distance between the transmitter and receiver, the more the signal spreads out

    so again, no, cannot be done in a lossless way

    Dave
     
  9. May 19, 2015 #8
    If we make the source of radiation, say a lens or concave mirror, large in size, the beam will be narrow, but will still diverge due to diffraction. At close distances, however, the beam is approximately parallel, and so the propagation between two mirrors can be nearly loss free. The distance for which the beam remains parallel is the Rayleigh Distance, and is approximately = Diameter^2 / (2 lambda). This distance also corresponds with the furthest point at which a lens or mirror may be focused.
    As a matter of interest, if the distance between the lenses or mirrors is not too great, it is possible to have a parallel beam and to convey nearly all the energy. In the London Science Museum, they have an optical waveguide consisting of a long pipe with a sequence of lenses, so you can see small objects several metres away. The lenses or concave mirrors must be closer than the Rayleigh Distance, which is approximately,
    = Diameter^2/(2 Lambda), and is the maximum distance at which a lens or mirror can form a focus. Optical waveguides like this were proposed for communication just before optical fibre became practicable.
     
  10. May 19, 2015 #9
    Vanadium answered this fine with their second post. Just point a flashlight at a photovoltaic cell. Or use a laser if you want something better collimated.
     
  11. May 19, 2015 #10

    davenn

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    The OP didn't want to use light

    he hinted that he wanted to use RF .... hence why I went into directional antennas
     
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