1-15
Figure 1-18.—Magnetic field in a waveguide three half-wavelengths long.
BOUNDARY CONDITIONS IN A WAVEGUIDE.—The travel of energy down a waveguide is
similar, but not identical, to the travel of electromagnetic waves in free space. The difference is that the
energy in a waveguide is confined to the physical limits of the guide. Two conditions, known as
BOUNDARY CONDITIONS, must be satisfied for energy to travel through a waveguide.
The first boundary condition (illustrated in figure 1-19A) can be stated as follows:
For an electric field to exist at the surface of a conductor it must be perpendicular to the conductor.
Figure 1-19A.—E field boundary condition. MEETS BOUNDARY CONDITIONS.
The opposite of this boundary condition, shown in figure 1-19B, is also true. An electric field
CANNOT exist parallel to a perfect conductor.
