The effect of surface roughness on electromagnetic propagation through rect
angular waveguide is studied using Finite Element Method. The effect of sur
face roughness on TE10, TE20 mode cutoff frequencies and passbands is studi
ed. The surface roughness on the walls of the waveguide has been generated
by using the RND function in Turbo Basic. The random variation in cutoff fr
equencies for TE10, TE20 mode is observed. The passband decreases with incr
ease in surface roughness.