for a travelling wave in a uniform waveguide at a given frequency and for a given mode, the distance along the longitudinal axis between adjacent points at which a field component differs in phase by 2p radians Found on http://www.electropedia.org/iev/iev.nsf/display?openform&ievref=726-05-01
for a travelling wave in a uniform waveguide at a given frequency and for a given mode, the distance along the longitudinal axis between adjacent points at which a field component differs in phase by 2p radians