propagation on the line is $c,$ find the maximum transmission line velocity of wave

$($a$)f=60Hz,$

$($b$)f=13kHz,$

$($c$)f=400MHz,$ and

$($d$)f=2\mathrm{.}5GHz.$

Answers:

$($a$)l_{\text{m}\text{a}\text{x}}=m$

$($b$)l_{\text{m}\text{a}\text{x}}=m$

$($c$)l_{\text{m}\text{a}\text{x}}=m$

$($d$)l_{\text{m}\text{a}\text{x}}=,m$