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Wave optics

  1. Oct 31, 2013 #1
    Why no backward wavefront is possible?
     
  2. jcsd
  3. Oct 31, 2013 #2

    ZapperZ

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    This is puzzling. A "mirror" is a "wave optics" device, and a reflection is a "backward wavefront".

    Zz.
     
  4. Oct 31, 2013 #3
    In a book it is written
    " there cannot be backward flow of energy during propagation of a wave..
    and the resultant amplitude of all secondary wavelets at any point on a backward wavefront is zero.
    The effects of secondary wavelets cancel out at all points except those lying on forward envelope. So a backward wavefront cannot exist.."

    I'm not able to understand this thing
     
  5. Oct 31, 2013 #4

    ZapperZ

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    In the future, you should start with this, and not the cryptic first post. Furthermore, in this forum, we require that you cite your source. So if you read it off a book, then the proper way to do this is to provide the author and title of the text.

    What your book described is ordinary material, having a "regular", normal index of refraction. But if you are still asking on if it is possible to have a material producing a "backward" wave, then yes, it is. There are a certain class of "metamaterial" that produced a negative index of refraction, often also called left-handed material.

    http://www.metamaterials.duke.edu/what-are-negative-index-refraction-materials [Broken]

    Note that these are more "exotic" type of material that are not usually cover in standard, optics text.

    Zz.
     
    Last edited by a moderator: May 6, 2017
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