An electromagnetic wave in vacuum has the electric and magnetic field \(\vec{E}\) and \(\vec{B}\), which are always perpendicular to each other. If the direction of polarization is given by \(\vec{X}\) and that of wave propagation by \(\vec{k}\), then:
1
\(\vec{X}\parallel\vec{B}\) and \(\vec{k}\parallel\vec{B}\times\vec{E}\)
2
\(\vec{X}\parallel\vec{E}\) and \(\vec{k}\parallel\vec{E}\times\vec{B}\)
3
\(\vec{X}\parallel\vec{B}\) and \(\vec{k}\parallel\vec{E}\times\vec{B}\)
4
\(\vec{X}\parallel\vec{E}\) and \(\vec{k}\parallel\vec{B}\times\vec{E}\)