Wednesday, September 4, 2019

electromagnetism - How is the conservation of energy formulated for electromagnetic waves?


The electromagnetic radiation consists of electric $\boldsymbol E(t)$, and magnetic $\boldsymbol B(t)$ fields. The magnetic and electric fields disappear and acquire max values at the same time points.


My question is how energy disappears and appears again, where does it go? The Poynting vector is just average value over a half of cycle.


How is energy conserved if we do not take an average? A photon on the other hand has constant energy of: $$E_p=\hbar\omega$$





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