# Energy conservation in plane wave

In plane wave the H and E are in phase. So the pointing vector disappears regularly every pi. How is energy conservation validated ? Is it through the uncertainty of energy and time ?

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I suspect you are looking at the wave in a static view (at a single $t$). Consider it's evolution in time. There are nodes but like the anti-nodes they move. –  dmckee Aug 27 '13 at 3:16