Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

How to determine where the B feild starts

  1. Dec 16, 2011 #1
    Hello,
    This is kind of a simple question but if an EM wave is propagating in the positive x direction and the E field starts in the positive z direction, how do you figure out if the B field starts in the - or + y direction?

    Thanks
     
  2. jcsd
  3. Dec 16, 2011 #2

    Simon Bridge

    User Avatar
    Science Advisor
    Homework Helper
    Gold Member
    2016 Award

    Have a look:
    http://en.wikipedia.org/wiki/Electromagnetic_radiation#Wave_model

    in the article, v is in the +y dir, +E is in the +z dir, so B is in the +x direction.
    to get your situation, rotate the axis anti-clockwise about +z ... now v is in the +x direction and B starts out in the -y direction.

    The relationship depends on the cross product in the wave equation.
    (Scroll down the link for derivation.)

    note: the end-on animation shows the view looking down the direction of v.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: How to determine where the B feild starts
  1. How light starts (Replies: 2)

Loading...