For a plane travelling EM wave, the correct equation for characteristic impedance Z for the medium with permittivity of $$\epsilon$$ and permeability of $$ \mu $$ is :

A

$$Z = \sqrt{\frac{\mu}{\epsilon}}$$

B

$$Z = \sqrt{\frac{\epsilon}{\mu}}$$

C

$$Z = \sqrt{\mu * \epsilon}$$

D

$$Z = \frac{1}{\sqrt{\mu * \epsilon}}$$