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!

A 200 mW horizontally polarized laser beam

  1. Jul 2, 2009 #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

    E (transmitted) = E (incident)cos()

    3. The attempt at a solution
    200= E(incident) cos (25)
    E(incident) = 2.206*10^2

    Not sure if this is correct..this is my last attempt at the question, need to know if I'm approaching this correctly at all?!?!
    Thanks!
     
  2. jcsd
  3. Jul 2, 2009 #2

    Doc Al

    User Avatar

    Staff: Mentor

    (1) Don't mix up the amplitude (E) with the intensity (what you want), which is governed by the Law of Malus. See: http://hyperphysics.phy-astr.gsu.edu/hbase/phyopt/polcross.html#c3"
    (2) The incident power is given; that's what the 200 mW refers to.
    (3) Note that the incident wave is horizontally polarized, while the angle given is with respect to the vertical.
     
    Last edited by a moderator: Apr 24, 2017
  4. Jul 2, 2009 #3
    so instead, if i understand you...it should be 200*cos(25) = 1.81*10^2???
     
  5. Jul 2, 2009 #4

    Doc Al

    User Avatar

    Staff: Mentor

    No, but you're getting closer. Read all three of my points, not just the second one.
     
  6. Jul 2, 2009 #5
    so in regards to #3...instead of being 25 degrees...it would be 65 degrees?? if i'm picturing this correctly
     
  7. Jul 2, 2009 #6

    Doc Al

    User Avatar

    Staff: Mentor

    Yes, that's what I would say.
     
  8. Feb 28, 2011 #7
    200*cos(65) = 84.5 =/= An answer Mastering Physics will mark as right.
     
  9. Mar 1, 2011 #8

    Redbelly98

    User Avatar
    Staff Emeritus
    Science Advisor
    Homework Helper

    See Doc Al's link to the Law of Malus in Post #2. What does the link say about the transmitted intensity? (Don't confuse it with the electric field.)
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: A 200 mW horizontally polarized laser beam
  1. Laser beam (Replies: 1)

  2. Laser Beam (Replies: 1)

  3. Polarized beam (Replies: 2)

Loading...