HSC Physics Cavity Resonance Measurement of the Speed of Light

Some questions on the measurement of the speed of electromagnetic waves using standing waves in a cylindrical metal cavity are given below. The method is that of Essen and Gordon-Smith (1947).

  1. How can a cylindrical cavity have a resonant frequency?
  2. Essen and Gordon-Smith (1947) state the following equation for the speed of electromagnetic waves in an evacuated cylindrical cavity. What do the symbols mean?