The electric field of a plane electromagnetic wave in a medium is given by

$$ \overrightarrow{\mathrm{E}}(x, y, z, t)=\mathrm{E}_0 \hat{\mathrm{n}} \mathrm{e}^{i k_o[(x+y+z)-c t]} $$

where $$\mathrm{c}$$ is the speed of light in free space. $$\overrightarrow{\mathrm{E}}$$ field is polarized in the $$x-\mathrm{z}$$ plane. The speed of wave is $$v$$ in the medium. Then