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Three polarizers

  1. Apr 4, 2016 #1
    1. The problem statement, all variables and given/known data

    Polarizers 1 and 3 have their axes of polarization, indicated by the black solid lines, perpendicular to each other. If you try to shine light through only the combination of 1 and 3, you will find that none passes through. However, now we put in another polarizer (number 2 in the figure) between number 1 and number 3. This polarizer has an axes of polarization that has an angle of θ = 42° with respect to the polarization axes of polarizer 1. Surprisingly, now some light passes through the combination 1+2+3. What percentage of the initial (unpolarized) light intensity passes through?

    2. Relevant equations
    I=I(nought) * cos^2 (theta)

    3. The attempt at a solution
    1. 100/2 = 50
    2. 50*cos^2(90-Angle given)= x
    3. x*cos^2 ((90-angle given)-angle given)= Answer
     
  2. jcsd
  3. Apr 4, 2016 #2

    DrClaude

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    Staff: Mentor

    Can you explain your thinking here?
     
  4. Apr 4, 2016 #3
    We had had a similar problem but using only two polarizers so I was thinking after the first one the same ideas could be applied for the last two.
     
  5. Apr 4, 2016 #4

    DrClaude

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    Staff: Mentor

    I don't understand why you take "90 - Angle given".
     
  6. Apr 4, 2016 #5
    Would it just be angel given then?
     
  7. Apr 4, 2016 #6
    Okay you pointing out how stupid I was being really helped, I got it! Thank you
     
  8. Apr 4, 2016 #7

    DrClaude

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    Staff: Mentor

    I would have said "distracted" :smile:

    Be careful when using solutions from other problems that you are applying them correctly for the problem at hand.
     
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