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Optics -- caustic curve equation

  1. Feb 5, 2015 #1
    I went through this article:
    http://users.df.uba.ar/sgil/physics_paper_doc/papers_phys/ondas_optics/caustica1.pdf [Broken]
    But I think that when we do F=0, we are assuming the centre of the curve to be the origin and assuming the curve to be a circle, because only then will we be able to say that OP=ON (i.e. F=0)..either the article has some issues or I am interpreting it wrongly..please help..
    Last edited by a moderator: May 7, 2017
  2. jcsd
  3. Feb 5, 2015 #2

    Andy Resnick

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    What the author did is simply re-write r = R cos() sec() as r-R cos() sec() = 0. For technical reasons, it's often easier to work with equations like F = 0 instead of r = something, especially if you are talking about the geometry of surfaces.

    Caustics are really fun to study (IMO)- check this out:

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