Surface impedance - Boundary condition

Click For Summary
SUMMARY

The discussion centers on the concept of surface impedance in relation to electromagnetic waves incident on a boundary between free space and a lossy medium. Specifically, it addresses the equations governing the electric and magnetic fields, particularly when a plane wave is normally incident versus obliquely incident on the surface. The relationship between tangential electric and magnetic fields is defined by the surface impedance, which is a complex quantity that accounts for medium losses. The forum participants explore how normal field components interact with surface impedance under oblique incidence.

PREREQUISITES
  • Understanding of Maxwell's equations
  • Familiarity with Helmholtz equations
  • Knowledge of electromagnetic wave propagation
  • Concept of surface impedance in lossy media
NEXT STEPS
  • Research the derivation of surface impedance from Maxwell's equations
  • Study the effects of oblique incidence on electromagnetic wave behavior
  • Explore the relationship between tangential and normal field components at boundaries
  • Learn about complex wave impedance in various media
USEFUL FOR

Electromagnetic engineers, physicists, and students studying wave propagation and boundary conditions in lossy media will benefit from this discussion.

EmilyRuck
Messages
134
Reaction score
6
Hello!
Let a plane wave propagate towards the -y direction. It is normally incident upon the plane (x,z) (whose normal unit vector is the y-direction unit vector, \mathbf{\hat{u}}_y): the plane represents the interface between the free space (in y > 0) and a general lossy medium (in y < 0).
We can say that, in general, for y < 0

E_z = - \eta H_x
E_x = \eta H_z

where \eta \neq \eta_0 (\eta_0 is the free-space wave impedance); \eta is a complex quantity which considers the losses of the medium.
This is obtained from Maxwell and Helmholtz equations. But what could happen if the plane wave is not normally incident upon the plane (x,z)?
Which field components will remain and propagate in the y < 0 region? And can we say that the interface has the boundary condition

\mathbf{\hat{u}}_y \times \mathbf{E} = \eta \mathbf{\hat{u}}_y \times (\mathbf{\hat{u}}_y \times \mathbf{H})

?
Why only the tangential components of the field are involved in these conditions?
Thank you for having read!

Emily
 
Physics news on Phys.org
Ok, I try to change the question:
The surface impedance on a conductor relates the *tangential* electric field to the *tangential* magnetic field, according to the preceeding expression. But what if a wave has an oblique incidence upon the conductor's surface? The components of the fields in the wave are not only tangential to the surface, but also normal: how are these normal components related to the surface impedance?

Emily
 
In sci-fi when an author is talking about space travellers or describing the movement of galaxies they will say something like “movement in space only means anything in relation to another object”. Examples of this would be, a space ship moving away from earth at 100 km/s, or 2 galaxies moving towards each other at one light year per century. I think it would make it easier to describe movement in space if we had three axis that we all agree on and we used 0 km/s relative to the speed of...

Similar threads

  • · Replies 3 ·
Replies
3
Views
2K
  • · Replies 1 ·
Replies
1
Views
1K
  • · Replies 22 ·
Replies
22
Views
3K
Replies
2
Views
2K
  • · Replies 4 ·
Replies
4
Views
2K
  • · Replies 3 ·
Replies
3
Views
506
  • · Replies 0 ·
Replies
0
Views
1K
  • · Replies 11 ·
Replies
11
Views
3K
Replies
4
Views
2K
  • · Replies 9 ·
Replies
9
Views
6K