Whenever you're dealing with current, you have to pay attention to the
definition of positive direction. If you define the positive direction
of forward current as being toward the load and of reflected current
toward the source, then Vf is in phase with If and Vr is in phase with
Ir. I suspect that a similar caution needs to be heeded when dealing
with optics.

Roy Lewallen, W7EL

Cecil Moore wrote:
Walter Maxwell wrote:

Sorry, Cecil, the phase between reflected voltage and current is
always 180
degrees, not zero.


Yep, I know better, I just mis-spoke. Did you know that there is no
such convention for light? It's Kirchhoff's current convention that
dictates a 180 degree phase between reflected voltage and reflected
current. EM light doesn't follow Kirchhoff's convention.

For EM light, there is no phase shift in the reflection if the index
of refraction is higher. If the index of refraction is lower, there
is a 180 degree phase shift in both E and H fields.