Explanation

(a) The impedance of free space $Z_{0}$ is a physical constant with a defined value that relates the magnitudes of the electric and magnetic fields of electromagnetic radiation travelling through free space.
$ie,\ \ Z_{0} = \left| \frac{E}{H} \right|$
$Z_{0} = \sqrt{\frac{\mu_{0}}{\varepsilon_{0}}} \approx 376.7\ \Omega$