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Snell optics problem

  1. May 6, 2009 #1
    1. The problem statement, all variables and given/known data
    The block of glass n = 1.5 shown in cross section in the figure (Intro 1 figure) is surrounded by air. A ray of light enters the block at its left-hand face with incident angle Θ1 and reemerges into the air from the right-hand face directed parallel to the block's base.
    Determine Θ1

    http://session.masteringphysics.com/problemAsset/1090003/2/GIANCOLI.ch32.p46.jpg
    2. Relevant equations
    n1 sin Θ1 = n2 sin Θ2 = n1 sin Θ3


    3. The attempt at a solution
    3. n1 sin Θ1 =n2 sin Θ2 = n1 sin Θ3
    n1 =1, n2=1.5, Θ3=45
    1 sin 45 = 1.5 sin(x) x= 28.125
    1.5 sin 28.125 = 1 sin(x) x = 45
     
  2. jcsd
  3. May 6, 2009 #2

    tiny-tim

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    Welcome to PF!

    Hi Sith Lord 13! Welcome to PF! :smile:

    Don't forget that Θ2 on the left face isn't the same as Θ2 on the right face. :wink:
     
  4. May 6, 2009 #3
    Re: Welcome to PF!

    Thank you.

    Why aren't they the same? And how do I determine what the left is then?

    Thanks
     
  5. May 7, 2009 #4

    tiny-tim

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    Because the left and right sides aren't parallel …

    so the internal angle (to the normal) at which the same ray meets the left side isn't the same as the internal angle at which it meets the right side :smile:

    just use a bit of geometry to work out how they're connected. :wink:
     
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