The skin depth at $10\; \mathrm{MHz}$ for a conductor is $1 \; \mathrm{cm}$. The phase velocity of an electromagnetic wave in the conductor at $1,000 \; \mathrm{MHz}$ is about
- $6 \times 10^{6} \mathrm{~m} / \mathrm{sec}$
- $6 \times 10^{7} \mathrm{~m} / \mathrm{sec}$
- $3 \times 10^{8} \mathrm{~m} / \mathrm{sec}$
- $6 \times 10^{8} \mathrm{~m} / \mathrm{sec}$