Richard Clark wrote:
"There is no such thing as cancelled energy short of a Nuclear folding
of the universe."

Most would agree to energy conservation.

Young`s experiment produces alternating bright and dark nands.

The bright bands are brighter because they contain redirected power that
would have appeared in the dark bands as well as the power idirectly
lluminating the bright bands. In the bright band spaces, power is
in-phase from both source slits. In the dark spaces, power is
180-degrees put of phase between the illuminations from the two slits.
This is caused by the distances from the two sources.

At the risk of diverting attention from the topic, I`ll indulge in
analogy. An impedance bridge has a null meter to indicate balance.
Superposition says a circuit with two (or more) sources may be analyzed
(with proper restrictions) as if there were only one source in the
system. That is, respones to the various sources may be analyzed
separately to determine the overall circuit response.

A balanced bridge may be considered as two voltage dividers set for the
same ratio and providing identical voltages to each terminal of the null
meter. Each divider taken alone provides the same fractiom of the bridge
generator`s voltage. Alone, each divider can supply current through the
null meter.

Equal and opposite ciurrents don`t flow through the null meter. No
current flows through the null meter because with equal and opposite
voltages on each side of the null meter there is no difference of
potential to evoke a current flow.

Given a perfect transmission line with a complete reflrction, a length
can be found which produces a reflection with with the same phase and
magnitude as that of the generator. With equal and same phase volts on
either side of the generator/line junction, current does not flow. No
potential exists to evoke a current flow. This is the same as a very
high impedance indeed.

Best Regards, Richard Harrison, KB5WZI