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Homework Help: Grade 12 physics problems

  1. Dec 8, 2004 #1
    Grade 12 physics problems :(

    One question:

    Because of absorption, a Polaroid will actually transmit 40% of nonpolarized light incident on it. Two such Polaroids with their axes aligned will transmit
    a. 16%.
    b. 24%.
    c. 30%.
    d. 32%.
    e. 40%.

    The answer is 32% and I have no cue why. My textbook doesn't say anything and since I am taking a conceptual physics course, I have no formulas to work with. Does anyone know why this is the answer?

  2. jcsd
  3. Dec 8, 2004 #2


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    Science Advisor
    Homework Helper

    An ideal polarizer will let 50% of the unpolarized light through.
    These polarizers in the problem are not ideal, they absorb a fraction/percentage of the light they should let through. Can you find this fraction to be 0.8?

    After that, since the light which went through the first polarizer is now linearly polarized in the direction of the second polarizer, the second polarizer should let all light through if it was ideal. But it again stops 80% if the light which is incident upon it.
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