waveguide attenuator theory?

A rectangle waveguide with a resistor film putting in middle of wide edge. This resistor could rotate,thus control the attenuator value. Book said only electical field parallel to resistor film would be absorbed. Could anybody explain it? Thanks.[/img]

Hi rachel_zh

I tried to simulate attenuator and termination for waveguide components.

Please check attached file. I think you can get any idea.

Have a good time!