The value of characteristic impedance in free space is equal to

• A. \(\sqrt {\frac{{{\mu _0}}}{{{\varepsilon _0}}}} \)
• B. \(\sqrt {{\mu _0}{\varepsilon _0}} \)
• C. \(\sqrt {\frac{1}{{{\mu _0}{\varepsilon _0}}}} \)
• D. \(\sqrt {\frac{{{\varepsilon _0}}}{{{\mu _0}}}} \)