- #1

frustrationboltzmann

- 5

- 2

Im trying to do a simulation of a poynting vector of an electromagnetic wave and I assume the following: At t=0 the E-field vector is (0,0,e^(-ikx)) and the H-field vector (0,e^(-ikx),0), hence orthogonal to it in vaccum, which is assumed, also the amplitudes are simplified both to 1 since only the direction is of interest.

When I calculate the cross product I get now: (-e^(-i2kx),0,0) and when I take the real part I get (-cos(2kx),0,0) which means the poynting vector oscillates in x-direction but this is wrong because it shouldn't oscillate.

My procedure was summarized: take the COMPLEX E-and H-vector, calculate the cross product and after get the real part of it...but this is obviously wrong.

if I take the real parts immediately of the 2 amplitudes and THEN take the cross product of the real amplitudes it works...I get a vector (cos(kx)^2,0,0) which also oscillates but not in 2 different directions but only in intensity which is correct.

between those 2 procedures is a contradiction but at the moment I am afraid I can't see why.

I appreciate any help.

Thank you in advance very much.