Question

In a waveguide, which of the following condition is true always?

(a) phase velocity = c

(b) group velocity = c

(c) phase velocity > c

(d) phase velocity < c

This question was addressed to me during an interview for a job.

My doubt stems from Phase and Group Velocity topic in division Waveguides of Electromagnetic Theory

Answer 1

Right option is (c) phase velocity > c

Explanation: The phase velocity is always greater than the speed of light in waveguides. This implies the group velocity is small.