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

Two sets of waves in a Hertzian Dipole?

  1. May 29, 2009 #1
    In the near field, a hertzian pole has a changing electric field and a changing magnetic field, that are in both space and time quadrature. Are two sets of EM waves then created in the far field, one from the changing e-field, and one from the changing m-field?
  2. jcsd
  3. May 29, 2009 #2
    There is only one radiated wave; The radiated Poynting vector P = E x H requires both an E vector and an H vector in phase. A quadrature phase field is an induction field (like in Faraday induction, where voltage is proportional to dB/dt), and cannot radiate power. The far-field radiated wave has the E:H vector ratio of 377:1 in the mks system. The polarization is along E.
    Last edited: May 29, 2009
  4. May 29, 2009 #3
    Don't the changing induction fields create the radiating far fields, as described by Maxwell's equations?
  5. May 29, 2009 #4
    If two fields are in time (phase) quadrature, They represent energy storage, not power. The integral of [sin(wt) x cos(wt) dt] over 2 pi is zero. Consider the voltage and current for a pure inductance. They are in phase quadrature, and there is no real power.
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook