Rectangular electromagnetic waveguide
= Rectangular electromagnetic waveguide
A rectangular electromagnetic waveguide has a vacuum interior bounded by four <perfect conductor> walls parallel to its axis. The harmonic fields obey zero tangential <electric field> and zero normal <magnetic field> at the walls. <Maxwell equations> determine transverse fields from longitudinal components; a purely longitudinal oscillating <magnetic field> by itself cannot propagate, since its divergence would be nonzero.