classical electrodynamics - national chiao tung...
TRANSCRIPT
Contents
§8.1 Fields at the Surface of and Within a Conductor
§8.2Metallic Cavities and Waveguides
A. The definition of and in terms of and
B. of TM mode, TE mode and in the
C.
Contents
§8.3 Energy Flow and Attenuation in Waveguides
A.
B. The field energy per unit time
C. 、 、
D. Attenuation;
§8.4 Multimode Propagation in Optical Fibers
A. 、 、
C.
D. 、 、 、
Contents
§8.5 Modes in Dielectrics Waveguides
A. Find
B. in geometrical optics
C. Find by Helmholtz equation
§8.1 Fields at the Surface of and Within a Conductor
From the boundary conditions we see that just outside the surface of a perfect
conductor only normal E and tangential H fields can exist, and that the fields drop
abruptly to zero inside the perfect conductor.
The fields in the neighborhood of the surface of a good, but not perfect, conductor
must behave approximately the same as for a perfect conductor. In Section 5.18 we
saw that inside a conductor the fields are attenuated exponentially in a characteristic
length δ, called the skin depth.
The existence of a small tangential component of E outside the surface, in addition to
the normal E and tangential H, means that there is a power flow into the conductor.
The time-averaged power absorbed per unit area is power loss