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Converging wave interference generating a caustic

  1. Sep 2, 2013 #1
    Dear reader, I have written a paper which I require a reference for converging wave interference generating a caustic.

    When studying for my degree, I performed Young's double slit experiment with the addiction of a converging lens. I was trying to comprehend Afshar's conclusion/interpretation of the copenhagen agreement. When I placed the converging lens at one focal length from the illuminated double slit, the converging wave interference generated a caustic which beamed an image of the double slit to infinity. Stunned and amazed by this property of nature, I informed my professor. He quickly referred to Fresnel's equations as the explanation and that this was a well understood phenomena. My paper is base on this property of nature yet I can not find any reference to, or any indication that the physics community is currently aware of this phenomena.

    Please help.

    Thank you for any time and effort spent, Darrell.
     
  2. jcsd
  3. Sep 2, 2013 #2

    Simon Bridge

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    Welcome to PF;
    ... so you figure that nobody but you and your physics professor know about this? Oh, and Fresnel presumably.

    I think what you are referring to is part of the normal formation of caustics.
    http://www.pma.caltech.edu/Courses/ph136/yr2012/1207.1.K.pdf
     
  4. Sep 3, 2013 #3
    Thanks for your quick reply, however I was referring to the phenomena of converging interfered waves forming an image at the caustic, which then "beams" to infinity. The reference you provide does not cover this phenomena. Please check link provided for a diagram.

    http://i.imgur.com/mXAGsrr.png
     
  5. Sep 3, 2013 #4

    Simon Bridge

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    No, I mean what you have observed is a natural consequence of the established physics.
    I'm afraid the diagram doesn't mean much to me. If you put origin of radially diverging light at the focus of the converging lens, wouldn't you expect the light to exit the lens parallel? Perhaps that's not what you meant to draw?

    Did you find the same work but ch8.6 for diffraction at the caustic?
     
  6. Sep 3, 2013 #5
    Please recall "stunned and amazed" I did expect the light to exit the lens parallel and whats more important is the obvious change of direction at the caustic. The diagram depicts what I observed. I have performed this experiment many times to astonish others. It is as if interfered waves become coherent at the caustic. I have check ch 8/9. there is no mention of a change in direction of the photon at the caustic. There is only construction and destruction of a caustic by ray/photon interpretation, which struggles to explain the beaming to infinity property observed. Optical reversibility still holds though.

    However, thank you, I will study ch8.6 as the words "diffraction at the caustic" are used in my paper to describe what I have observed. I expect manipulating the Airy function to model the experiment might show something.
    Darrell
     
  7. Sep 3, 2013 #6

    Simon Bridge

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    Why do you expect a change in direction of the photon at the caustic?
    You should remember the wave nature of light.

    You have observed bright fringes radiating from the slits to the lens, then converging from the lens to the caustic. Beyond the caustic ... is the image two bright fringes consistent with the slit dimensions?
     
  8. Sep 3, 2013 #7
    As you have already pointed out; if a radiant source is placed at one focal length from a converging lens, parallel waves are the result. If this is true, how do these waves interfere? Also, the diverging interference pattern results from diverging waves yet the converging interference pattern is generated by parallel waves. This does not seem consistent with optical reversibility.

    However, as far as I can tell, what you are generally saying is that the wave nature I observed is indeed a well understood phenomena and does not require a reference within a paper.
     
  9. Sep 4, 2013 #8

    Simon Bridge

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    Didn't you have a look at how Fresnel's equations work for this?
    Whether you need a citation depends on the role it plays in your writing.
     
  10. Sep 4, 2013 #9

    Chronos

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    I also suggest taking a look at Fresnel's thousand slit experiment.
     
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