An electromagnetic wave travelling in a lossless dielectric medium having a dielectric constant,
\[
\varepsilon_r = 9,
\]
has the electric field
\[
E_x=E_0\sin(kz-2\pi\times10^6 t)\ \text{V m}^{-1}
\]
where \(E_0\) is the amplitude and \(k\) is the wave vector.
Among the following options, the incorrect choice is: