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Effect of rotating polarizer on intensity of transmitted light

  1. Jan 12, 2016 #1
    1. The problem statement, all variables and given/known data

    Plane polarised is incident normally on a polerizer which can rotate in plane perpendicular to light. The intensity of of incident light is 8W[m][/-2] and transmitted intensity is 2W[m][/-2] if polerizer is rotated 90 deg what is the new transmitted intensity
    2. Relevant equations


    3. The attempt at a solution
    Root of (8 squared minus 2 squared)=root 60
    Resolving vectors?
    Answer was 6W[m][/-2]
    Which is just eight minus two, help? I dont know why
     
    Last edited by a moderator: Jan 13, 2016
  2. jcsd
  3. Jan 12, 2016 #2

    gneill

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    Staff: Mentor

    What is the law for polarizers? In other words, what relevant equation applies to polarizers?
     
  4. Jan 13, 2016 #3
    Transmitted intensity = incident intensity times cosine there
    Where theta is the angle between the direction of the polerizer and the polarised light
     
  5. Jan 13, 2016 #4

    gneill

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    Staff: Mentor

    Close, but not quite: the cosine should be squared. Look up "Law of Malus" (or Malus's Law).
     
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