Three polarizers

  1. 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 = 71° 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?


    The light passing through the
    first polarizer should be 0.5I(nought). The light passing
    through the second polarizer should be
    0.5I(nought)*cos^2(angle given). The light passing through
    the third polarizer should be the previous answer times
    cos^2(angle between axes 2 and 3...)

    My answer is not coming out right...Any suggestions of what
    I may be doing wrong?
     
  2. jcsd
  3. berkeman

    Staff: Mentor

    Are you using 71 degrees for the first angle and 90-71 degrees for the second angle?
     
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