The frequency of the power wave, associated with an electromagnetic wave, having a field as E = e−Z/δ cos \(\left(\omega t −\frac{Z}{\delta}\right)\), is given by
1
\(\frac{\omega}{4 \pi}\)
2
\(\frac{\omega}{\pi}\)
3
\(\frac{\omega}{8 \pi}\)
4
\(\frac{\omega}{2 \pi}\)