The problem is as follows :
The inside of part of a square aluminum metal guide ( = 1.00 and = 3.54 × 107 [S / m]) was infiltrated with water ( = 80 and = 4.00 [S / m]) after a severe thunderstorm. This affects the transmission from the source to the receiver for waves of carrier frequency f = 15 GHz. The guide does 10 m in length and has an interior section of 2 cm x 2 cm.
a) What was the fraction of the power transmitted between the source and the receiver for the dominant modes of the guide before the storm?
b) and after the storm if the infiltrated part is 1 cm long? (Assume the same value of fc as in a).)
I've managed to find a) but I can't seem to find b)
Can you guys help me ?