3cm x 4cm rectangular wave guide filled a non-conducting and non-magnetic material with 4. If the operating frequency equal to the average value of first two modes. Find the: a- Operating frequency (f) b- Values of B, Up, ug Ag and Z for the dominant mode c- Assume that the operating frequency is the result of section a, if material has , 16. Find the propagation modes and cut-off frequencies of these modes.