Cecil Moore wrote:

If an EM wave exists, it's
Poynting vector is ExM. The energy in that individual wave *must*
be conserved. If that energy is not conserved, the conservation
of energy principle is violated.

When a wave is canceled, there is no wave. Therefore there can be no
energy associated with that wave. If there is energy, then it must be
associated with a wave that is not canceled. Same thing is true when
I have candy. If it's not in my left hand, then it must be in my
right hand. It's all very profound.

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