The cavity resonators used in the reflex klystron oscillators are for
(a) Generating RF signals
(b) Generating microwave signals
(c) Amplifying RF signals
(d) Amplifying microwave signals
I have been asked this question by my school principal while I was bunking the class.
This intriguing question originated from Waveguide Current and Excitation topic in division Waveguides of Electromagnetic Theory