If the ratio of relative permeability and relative permittivity of...

\frac{\mu_r}{E_r}=\frac{1}{4} \frac{E}{H}=\frac{E \mu}{B}=v \mu =\frac{1}{\sqrt{\mu \varepsilon}} \mu=\sqrt{\frac{\mu}{\varepsilon}}=\sqrt{\frac{\mu_0 \mu_r}{\varepsilon_0 \varepsilon_r}} =\sqrt{\frac{\mu_0}{\varepsilon_0}} \sqrt{\frac{\mu_r}{\varepsilon_r}} =120 \pi\left(\frac{1}{2}\right)$=\frac{60 \pi}{1}$