1. Limited time only! Sign up for a free 30min personal 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!

Homework Help: Plane-polarized electromagnetic waves

  1. Aug 7, 2010 #1
    1. The problem statement, all variables and given/known data

    Consider a plane-polarised electromagnetic wave in source-free vacuum, with magnetic field B = (1,1,0)BoCos(kz-wt), with Bo = 0.001 Tesla. Find
    (1) the direction of propagation of the wave,
    (2) average energy density carried by the wave, and
    (3) the fraction of this energy which would pass through a perfect polariod sheet at normal incidence, if the angle between B and the transmission axis of the polariser is 30degrees.

    2. Relevant equations
    Uvpw = eoEo^2cos^2(kz-wt)
    eo = 8.854x10^-12
    Not really sure of any others

    3. The attempt at a solution
    (1)travelling in the +z direction
    (2)Bo=Eo/c Eo= 10^5
    <Uvpw> = eoEo^2x(average of cos^2) average cos^2 = 0.5
    <Uvpw> = 0.5eoEo^2 = 0.398Jm-3

    Im pretty sure the first two are right but im stumped how to do part 3.
  2. jcsd
  3. Aug 8, 2010 #2


    User Avatar
    Staff Emeritus
    Science Advisor
    Homework Helper
    Education Advisor

    A polarizer lets the component of the electric field parallel to the transmission axis through; it blocks the perpendicular component.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook