Roy Lewallen wrote:

The impinging field induces a current on the element. The current
produces a field which radiates. An AC current flowing on a conductor
creates a field regardless of how that current is produced. It doesn't
matter whether the current is due to conduction from a source, by
induction from a field, or any combination of the two -- the field
resulting from the current is exactly the same. Yagis and other
"parasitic" arrays depend entirely on this phenomenon for their operation.

Roy Lewallen, W7EL

Andy asks:
Roy, is the field radiated by the parasitic element shifted in phase
relative to the incident field. If not, what determines the phase
shift ?

Andy W4OAH