Solution
= Solution
The <parallel-plate transmission line> has per-length $C=\epsilon b/a$ and $L=\mu a/b$. The lossless <telegrapher's equations> imply wave speed $1/\sqrt{LC}=1/\sqrt{\mu\epsilon}$, independent of the much slower <electron drift velocity>.
Full derivation: <past-exam-of-the-physics-b-course-of-the-university-of-cambridge/2010/paper-2a/section-b/b8/solution>.