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Homework Help: Getting Brewster's Formula from Snell's Law

  1. May 1, 2012 #1
    From Snell’s Law equation (2) get the Brewster’s angle formula given by equation (4) when θincident+θrefracted=90°.

    equation 2: n1 sin θ1 = n2 sinθ2

    equation 4: tanθB = n2/n1

    This is kind of foreign to me as I haven't studied it yet, not sure how you go from Eq 2 to E4, how does tan come from an equation with 2 sin in it?
  2. jcsd
  3. May 1, 2012 #2
    You know that θ1 + θ2 = 90. Try subing in θ2 = 90 - θ1.
  4. May 1, 2012 #3
    so then I would eventually end up with:

    sinθ1/sin(90-θ1) = n2/n1

    still not sure how the left side turns into tanθb though...
  5. May 1, 2012 #4


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    Homework Helper

    Remember the definition of sine and cosine of the angles in a right triangle.

  6. May 1, 2012 #5
    Since you know the answer, you can take a peek at it and then look back at what you currently have. What must sin(90-θ1) to transform where you are into the answer? The next question is "does sin(90-θ1) equal what it needs to equal?"
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