"Cecil Moore" wrote in message
...
The 'why' is conservation of energy. If there are only two directions
available and energy was traveling in one direction and now it isn't,
it's a no-brainer to realize that it must have changed directions.

Cecil, I think a more convincing argument is that I can take a slotted line
and directly measure a standing wave on it. A wave traveling in one
direction can not do that. Or am I cunfusing things?

Tam/WB2TT