Cecil Moore wrote:
Consider the equation, rho = (ZL-Z0)/(ZL+Z0). If ZLZ0, then the
voltage reflection coefficient is positive and there is no reflected
voltage phase shift. If ZLZ0, then the voltage reflection coefficient
is negative and there is a 180 degree phase shift in the reflected
voltage. The same holds true for the E-field of reflected light.

The above assumes ZL and Z0 to be real numbers. The light index
of refraction is usually a real number.
--
73, Cecil, W5DXP