Question

If $\vec{E}$ and $\vec{B}$ are the electric and magnetic field vectors of e.m. waves then the direction of propagation of e.m. wave is along the direction of

• A. $\vec{E}$
• B. $\vec{B}$
• C. $\vec{E} \times\vec{B}$
• D. None of these

Answer 1

Answer: (C)

$\vec{E} \times\vec{B}$

Answer 2

we know that;
The direction of propagation of the electromagnetic wave is perpendicular to the plane of oscillation of electric and magnetic field of the EM wave.
Thus,
If, $\vec{E}$ and $\vec{B}$ are electric and magnetic field vectors of the EM wave, the direction of its propagation will be given by $\vec{E} \times \vec{B}$
As in an EM wave, the vectors $\vec{E}$ and $\vec{B}$ are perpendicular to each other, the direction of the wave propagation will be perpendicular to the plane containing the electric and magnetic field vectors.