Question

A wave is propagated in a waveguide at frequency of 9 GHz and separation is 2 cm between walls find cut off wavelength for dominant mode.

Answer 1

$f_c=\frac{c}{2a}=\frac{3\cdot 10^8}{2\cdot 2\cdot10^{-2}}=7.5 ~GHz.$

$u=\frac{c}{\sqrt{1-(\frac{f_c}{f})^2}}=5.43\cdot 10^8 \frac ms.$

$\lambda=\frac uf=\frac{5.43\cdot 10^8}{9\cdot 10^9}=6 ~sm.$