Question

The intrinsic impedance of a TM wave will be

(a) Greater than 377 ohm

(b) Equal to 377 ohm

(c) Lesser than 377 ohm

(d) Does not exist

The question was posed to me in semester exam.

My question is taken from Transverse Magnetic Waves(TM) in portion Waveguides of Electromagnetic Theory

Answer 1

Right option is (c) Lesser than 377 ohm

The best explanation: The intrinsic impedance of the transverse magnetic wave is given by ηTM = η √(1-(fc/f)^2). Here the term √(1-(fc/f)^2) is always lesser than unity. Thus the intrinsic impedance of the TM wave is lesser than 377 ohms.