chp38_14 - PHY2061 R. D. Field Energy Transport - Poynting...

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PHY2061 R. D. Field Department of Physics chp38_14.doc University of Florida Energy Transport - Poynting Vector Electric and Magnetic Energy Density: For an electromagnetic plane wave E y (x,t) = E 0 sin(kx- ω t) , B z (x,t) = B 0 sin(kx- ω t) , where B 0 = E 0 /c . The electric energy density is given by uEE k x t E == 1 2 1 2 0 2 00 22 εε ω sin ( ) and the magnetic energy density is uB c EE u BE = = 1 2 1 2 1 2 0 2 0 2 2 0 2 µµ ε , where I used E = cB . Thus, for light the electric and magnetic field energy densities are equal and the total energy density is uu u E B E k x t tot E B =+= = = µ εω 0 2 0 2 1 sin ( ) . Poynting Vector ( rr r SE B 1 0 ): The direction of the Poynting Vector is the direction of energy
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