Examples for

Waveguides are structures that guide electromagnetic waves with minimal loss of energy by restricting expansion to one dimension. When fully closed, they become resonant cavities that restrict the allowed waves even further. Wolfram|Alpha provides formulas for computing the allowed frequencies, their velocities and how the wave looks as it passes through the waveguide.

Compute properties of rectangular and circular waveguides.

Explore resonant properties of a rectangular cavity with or without a dielectric filling.