Q. 56 An air-filled rectangular waveguide of internal dimensions a cm 
b cm (a > b) has a cut-off frequency of 6 GHz for the dominant 
mode. For the same waveguide, if the cut-off frequency of the 
mode is 15 GHz, the cut-off frequency of the 
mode in GHz is _______.
Answer: (13.74)
Explanation:
