Wave equations & Polarization

Discussion in 'Homework Help' started by mo2015mo, Oct 13, 2013.

  1. mo2015mo

    Thread Starter Member

    May 9, 2013
    157
    1
    Hi my friends :) ,,

    I have two questions as follow

    1) Helmholtz’s equations for E & H are the same form so are the same soltuion
    Do it follow that E = H? Explain

    My answer is they don't equal in magnitude becuase as we know E = ηH ,, η denotes to intrinsic impedance between two fields
    Is this correct answer or not ?

    --------------------------------------------------

    2) Which of the following two descriptions defines an RHC (Right-Hand-Circular) polarized wave : A wave incident upon an observer is RHC polarized if its electric field appears to the observer to rotate in a counterclockwise direction
    (a) as a function of time in a fixed plane perpendicular to the direction of wave travel or (b) as a function of travel distance at a fixed time t ?

    here really i confused about it, What the difference between (a) & (b)?
    i have searched in google for this subject but i don't anything.

    please help me and thanks in advance :)
     
  2. mo2015mo

    Thread Starter Member

    May 9, 2013
    157
    1
  3. WBahn

    Moderator

    Mar 31, 2012
    17,748
    4,796
    The difference between (a) and (b) is simple. One is at a fixed location as time varies and the other is at a fixed time as location varies.

    Imagine you are standing next to a road that goes up and down across the rolling hill landscape it crosses. Their are a bunch of identical cars coming toward you down the road. If you look at a fixed location and consider the elevation of the car at that location as time passes, it never changes. But if you consider the elevation of the car at different locations as a given moment in time, it does change. Now imagine that you are doing this in an earthquake such that the road is oscillating up and down, too. You can picture that there are some combinations of where you look and when you look such that the elevation of the car you see is always the same, even though every car is moving up and down and every place on the road is moving up and down.
     
  4. mo2015mo

    Thread Starter Member

    May 9, 2013
    157
    1
    Okay, Thank u very much for this wonderful explanation...
    Based on that the correct answer to the second question is (a)

    What about my answer for fist question is correct or not ??
    \Is there a book or link helps me to understanding all states of polarization clearly ??
     
  5. WBahn

    Moderator

    Mar 31, 2012
    17,748
    4,796
    I don't think your answer to the first question is correct -- but I am drawing upon thirty year old memories making that statement. First off, isn't it the D field that is related to the E field, while the H field is related to the B field? IIRC, the relationships between D and E and those between H and B are due to the material properties of the medium.

    In LIH (linear, isotropic, homogenious) materials, I believe that D is proportional and parallel to E and that H is proportional and parallel to B. But I think this is not true in general, particularly in anisotropic and/or nonlinear materials.
     
  6. mo2015mo

    Thread Starter Member

    May 9, 2013
    157
    1
    i know this relations,, but the wave equations have the same form , so their solution the same implies H and E are have same magnitude ??

    My friends,, Do u know a book or link helps me to understanding all states of polarization clearly ??
     
  7. WBahn

    Moderator

    Mar 31, 2012
    17,748
    4,796
    Huh?

    How far I go in a certain about of time traveling as a certain speed is D=ST.

    The voltage across a certain resistor having a certain current in it is V=IR.

    Since these are of the same form, does this mean that D=V, or even D=kV?

    A very, very good book on electromagnetics is Electromagnetic Fields by Wangsness.
     
Loading...