Question: Q. 4. If $\vec{E}$ and $\vec{B}$ represent electric and magnetic field vectors of the electromagnetic wave, the direction of propagation of electromagnetic wave is along (a) $\vec{E}$. (c) $\vec{B} \times \vec{E}$. (b) $\vec{B}$.
(d) $\vec{E} \times \vec{B}$.
[NCERT Exemplar]
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Solution:
Ans. Correct option : (d)
Explanation: The direction of propagation of electromagnetic wave is perpendicular to $\vec{E}$ and $\vec{B}$ both and by right thumb rule.
The direction of propagation of electromagnetic wave is perpendicular to both the electric field vector $\vec{E}$ and $\vec{B}$ magnetic field vector $B$, i.e., in the direction of $\vec{E} \times \vec{B}$.
Here, electromagnetic wave is along the $z$-direction which is given by the cross product of $\vec{E}$ and $\vec{B}$.
