Physlet Illustration: Propagation of an Electromagnetic Wave

 

 

In this simulation, an electromagnetic wave propagates along the z direction. The electric field is displayed in blue and the magnetic field is displayed in red. The lengths of the E and B vectors are arbitrary, only direction and relative phase are important. You may click-drag in the animation to change the viewing angle. How are these varying fields related to each other and to the propagation of electromagnetic energy?

Hints:

  1. In what direction (x, y, or z) does the electric field oscillate?
  2. In what direction does the magnetic field oscillate?
  3. When E is a maximum (or minimum) at some point along the z axis, what is the value of B at that same point?
  4. What, then, do we call the phase relationship between E and B?
  5. In what direction do you see energy (and momentum) moving?

Reference

See Walker, Section 25-2

Illustration written by Steve Mellema