Think of the behavior of RF transmission lines. RF is after all just long wavelength light or EM waves.
So obviously a piece of pipe is a circular waveguide and it works more or less like optical fiber.
It helps if you know how optical fiber works, across a boundary with a big enough difference in speed of light in the material, you get total internal reflection and it bounces back in.
Now people are pretty chill with circular waveguide as a transmission line, but there are numerous other schemes and eventually you end up with microstripline or twin-lead that TVs used to use or eventually one wire Goubau line.
Once you're chill with a zillion small steps from circular waveguide to G-line, wait, G-line is what your prof said that initially sounded ridiculous, but its not so ridiculous after all, with some new perspective.
So obviously a piece of pipe is a circular waveguide and it works more or less like optical fiber.
It helps if you know how optical fiber works, across a boundary with a big enough difference in speed of light in the material, you get total internal reflection and it bounces back in.
Now people are pretty chill with circular waveguide as a transmission line, but there are numerous other schemes and eventually you end up with microstripline or twin-lead that TVs used to use or eventually one wire Goubau line.
https://en.wikipedia.org/wiki/Single-wire_transmission_line
Once you're chill with a zillion small steps from circular waveguide to G-line, wait, G-line is what your prof said that initially sounded ridiculous, but its not so ridiculous after all, with some new perspective.