Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

When the light enters calcite it is splitting in two rays

  1. Jun 20, 2011 #1
    When the light enters calcite it is splitting in two rays perpendicular polarized to each other ordinary and extraordinary,right?But then which ray is perpendicular to the optic axis and which are parallel.I do not understand this because some books say ordinary wave is perpendicular and extraordinary is parallel,but then wikipedia says oppositively that ordinary wave is perpendicular to optical axis and extraordinaty is parallel to it.Who is the right?Please give me right answer.And also which wave has greater velocity?Thanks
     
  2. jcsd
  3. Jun 20, 2011 #2

    Andy Resnick

    User Avatar
    Science Advisor
    Education Advisor
    2016 Award

    Re: Birefringence

    In uniaxial crystals, there is one special direction along the crystal axis of three- (trigonal), four- (tetragonal) or six-fold (hexagonal) symmetry (usually defined to be the 'z' direction). Then, the full dielectric tensor resolves into two components e_z and e_x = e_y. Biaxial crystals have no crystallographic-equivalent directions and e_x != e_y != e_z.

    In uniaxial crystals, waves that propagate in 'z' are extraordinary, while those the propagate in x and y are ordinary- ordinary waves propagate with a velocity independent of direction.

    If the crystal is positive uniaxial (quartz), then v_e < v_o, while negative uniaxial crystals (calcite) have v_e > v_o.
     
  4. Jun 20, 2011 #3
    Re: Birefringence

    I do not really quit understand that you have wrote,but i think i already found the answer and it like this:extraordinary wave will be parallel to the optical axis and ordinary wave will be perpendicular.be aware what is wrong description in wikipedia about birefringence
     
  5. Jun 20, 2011 #4
  6. Jun 20, 2011 #5

    Andy Resnick

    User Avatar
    Science Advisor
    Education Advisor
    2016 Award

    Re: Birefringence

    I didn't see anything obviously wrong in the Wiki entry. For example, see the table "Effective refractive indices in negative uniaxial materials" and the text "For a given propagation direction, there are generally two perpendicular polarizations for which the medium behaves as if it had a single effective refractive index. In a uniaxial material, rays with these polarizations are called the extraordinary and the ordinary ray (e and o rays), corresponding to the extraordinary and ordinary refractive indices."

    My only complaint about the wiki article is that it sometimes uses the term "optical axis" instead of "optic axis"- the "optical" axis refers to the direction of light propagation, and specifically the centerline of a rotationally symmetric optical system. The "optic" axis refers to the crystal orientation of a inhomogeneous optical material.

    http://en.wikipedia.org/wiki/Optic_axis_of_a_crystal
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: When the light enters calcite it is splitting in two rays
  1. Two Rays of Light (Replies: 5)

  2. Ray of light (Replies: 4)

Loading...