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Finding Incident Intensity for Unpolarized Light

  1. Sep 8, 2009 #1
    1. The problem statement, all variables and given/known data
    Two sheets of Polaroid are placed on top of each other with an angle φ between their pass
    directions. Calculate be the ratio of transmitted to incident intensity for initially unpolarised
    light if φ = 30°.


    I copied the question exactly, I'm pretty sure that typo wasn't on purpose but I left it there anyway.

    2. Relevant equations

    I0 = I'/2

    Malus's Law
    I = I0 cos^2 θ

    3. The attempt at a solution

    I used the equation above to do:

    = I0 cos^2(30)
    cos^2(30)=.75
    .75 x .75 = .5625 = 9/16
    = I0(9/16)

    not sure if that is right
     
    Last edited: Sep 8, 2009
  2. jcsd
  3. Sep 8, 2009 #2

    rl.bhat

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    Homework Helper

    When the unpolarised light is transmitted through a Polaroid, 50% of light is transmitted. So I' = Io/2
    When it passes through second Polaroid, the intensity of transmitted light is
    I" = Io/2*cos^2(θ)
     
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