1. The problem statement, all variables and given/known data How to solve this problem? An air-filled waveguide of rectangular cross-section (1 cm x 2 cm) is used to carry EM waves at a frequency of 10 GHz. Show that only the TE01 mode can be used? I tried to find the cut-off frequency ( 7.5GHZ) and is that enough to prove that only TE01 can be used?