Brian Reay wrote in :

A cross product of two vectors is a third vector orthogonal to the first
two. In the case of the EM wave, the E and H vectors are orthogonal so
the cross product is in the third dimension, the direction of propagation.


Ok, thanks. This reminds me of the Flemings 'hand rules', which I have never
been taught directly so have failed ot remember and have to look up on the
rare occasion I need to. Any relation? Or are those limited to motors and
generators?