1. Not finding help here? Sign up for a free 30min tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Polarization between 3 sheets intensity

  1. May 23, 2017 #1
    1. The problem statement, all variables and given/known data
    Hi guys I am having a problem with this question
    upload_2017-5-23_20-58-43.png
    Q55 a) and b)

    My problem is that for part a) I used the following logic. That if two sheet wont let light through at ##90^\circ## so if a 3rd sheet is inserted between the two the angle between each is ##45^\circ##, But for part a) ans b)seem to be getting something wrong. I assume the the light I will show my working below.
    2. Relevant equations
    ##I=I_0cos^2\theta##

    3. The attempt at a solution

    a) light from sheet 1 to sheet 2 is:

    ##I_{1,2}=I_0(cos45)^2=\frac{I_0}{2}##

    light from sheet 2 to sheet 3 is:

    ##I_{2,3}=\frac{I_0}{2}(cos45)^2=\frac{I_0}{4}##

    but the ans is \frac{I_0}{8}

    which is where I am confused is the first sheet be put at and angle of 45 degrees when light enters beacuse I was under the assumption the the first sheet is perpendicular to the last sheet at it is the sheet in the middle that is only 45 degrees.

    I am having the same issue with b) thus why I have no workings
     
  2. jcsd
  3. May 23, 2017 #2

    gneill

    User Avatar

    Staff: Mentor

    The ##I_o## in the law of Malus is usually taken to be the light intensity after the first polarizer. You need to first find out how that ##I_o## relates to the initial incident unpolarized light intensity :wink:
     
  4. May 28, 2017 #3
    Ah yes I see now, that on average the electric feild is 45 degree w/r to the trasmission axis. So the through the firs filter it would be ##I=I_0\frac{1}{2}##

    thank you very much for your help
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted