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Bi-refraction by calcite crystal

  1. Dec 9, 2004 #1
    When light passes through calcite crystal it splits into two rays, extra ordinary and an ordinary ray. Ordinary ray travels straight and extra ordinary ray is refracted. This would mean ordinary ray travels faster and e-ordinary ray travels slower because index of refraction is inversely proportional to speed. But somewhere (here) I read that calcite has an negative birefringence therefore ordinary ray travels slower. Can some1 explain this to me ?
    Last edited: Dec 9, 2004
  2. jcsd
  3. Dec 16, 2004 #2
    Well, the ordinary ray travels straight only at normal incidence. At other angles it is refracted according to Snell's law.

    The extraordinary ray is polarized perpendicular to the ordinary ray. Depending on its angle with respect to the optical axis, it travels at different velocities. In a Huyghens construction, the wavefronts are not spherical but ellipsoidal. This one can use to construct the direction of the extraordinary ray. Here is a .pdf with some figures:
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