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Intensity of Light With a Given Power of Through a Polarizer

  1. Apr 13, 2012 #1
    1. The problem statement, all variables and given/known data
    A 200 mW horizontally polarized laser beam passes through a polarizing filter whose axis is 25 degrees from vertical.

    What is the power of the laser beam as it emerges from the filter?
    P=mW

    2. Relevant equations

    I0cos2(theta)
    I≈E0cos(theta)
    I=E0cos2(theta)
    I=P/A=(E02)/(cμ0)=(cε0E02)/2

    3. The attempt at a solution
    I have tried numerous ways and I still cant seem to get it
    I'm almost positive you must use 65° instead of 25°, and I have ran out of ways for me to do this problem because I don't know how to get my Intensity because we don't know the Area, so I'm sort of stuck
    .2= E(incident) cos (65)
    E(incident)= .473 ---> wrong






    Thanks!
     
  2. jcsd
  3. Apr 13, 2012 #2

    Doc Al

    User Avatar

    Staff: Mentor

    Power and intensity are proportional, so just use your first equation (Malus's law).
     
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