Microwave Optics: Explaining Falling Amplitude with Reflector

[simo]

This is a question I came across in lab. I inserted a reflecter between a microwave transmitter and receptor, with the plane of the reflector parallel the the axis of the beam. The reflector is then moved away. See the setup and data plot in the attachment.

I understand that the waves are coming in an out of phase as you move the reflector which is why the plot oscillates. I also know that the further away the reflector, the less the receptor picks up because the waves diverges off the reflector. What I can't explain is why the amplitude of the wave falls to zero when the reflector is in the middle. Any ideas?

 

[BigJDubs]

The amplitude of the wave falling to zero when the reflector is in the middle is most likely due to destructive interference. This means that the waves that are being reflected off the reflector are 180 degrees out of phase with the original wave, which cancels out the signal. As the reflector is moved further away, there is less interference and the amplitude increases.