# TE Waves in Rectangular Wave Guide

1. Dec 29, 2013

### unscientific

Hi guys I'm having difficulty understanding why the boundary conditions lead to dX/dx = 0.

Why must Bx = 0 at x = 0 and x = a?

2. Dec 29, 2013

### Meir Achuz

B_n is continuous at a boundary, and B=0 inside a perfect conductor (which is assumed for these equations).
Therefor B_n=0 just outside the conductor.

3. Dec 29, 2013

### buoyant

And that is arisen from the fact that there is no magnetic dipole, i.e., the magnetic field is divergenceless. You can derive the continuity of the normal component of the magnetic field on the boundary by imaging a small pillbox on the boundary. Maybe Griffiths already described in Chap 5.

4. Dec 30, 2013

### Meir Achuz

I know you meant monopole.

5. Dec 30, 2013

### buoyant

Thanks Achuz for noticing my mistake

6. Jan 1, 2014

### unscientific

Sorry, I don't get what you mean. If B_n is perpendicular to surface and = 0, then won't Bx = 0 and By = 0 along y-axis and x-axis correspondingly

Last edited: Jan 1, 2014
7. Jan 1, 2014

### scoobmx

Only the normal component is continuous.. so B is parallel to surface at the boundary.

8. Jan 1, 2014

### unscientific

Yes, so along x-axis, By = 0, and along y-axis, Bx = 0?

9. Jan 1, 2014

### Meir Achuz

Yes................