Transverse electromagnetic (TEM) modes have
where is the angular frequency and c is the speed of light.
References
Budden, K. G. The Wave-Guide Mode Theory of Wave Propagation. Englewood Cliffs, NJ: Prentice-Hall, 1961.
Collin, R. E. Field Theory of Guided Waves, 2nd ed. New York: IEEE Press, 1991.
Huxley, L. G. H. Wave Guides.
Lamont, H. R. L. Wave Guides, 3rd ed., rev. London: Methuen, 1950.
Weisstein, E. W. "Books about Waveguides." http://www.ericweisstein.com/encyclopedias/books/Waveguides.html.
