
127Waveguides
modes can be explained in view of Equation 3.30a. According to this velocity
relation, there will be faster propagation of the lower-order mode and slower
propagation of the higher-order mode. Correspondingly, the wave will strike
the two walls more frequently in case of higher-order mode than in case of
the lower-order mode.
3.6.13 Group Velocity Variations
In view of Equations 3.18, 3.22 and 3.29, it is evident that both velocity ‘
υ
’
and wavelength ‘
λ
’ are inversely proportional to m and n. If the frequency ‘
ω
’
remains the same and m and n are increased (i.e., order of mode is higher),
the wave will progress at slower velocity