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Question: Answered & Verified by Expert
An electromagnetic wave in vacuum has the electric and magnetic fields $\vec{E}$ and $\vec{B}$, which are always perpendicular to each other. The direction of polarization is given by $\vec{X}$ and that of wave propagation by $\overrightarrow{\mathrm{k}}$. Then :
PhysicsElectromagnetic WavesJEE MainJEE Main 2012 (Offline)
Options:
  • A
    $\vec{X} \| \vec{B}$ and $\vec{k} \| \vec{B} \times \vec{E}$
  • B
    $\vec{X} \| \vec{E}$ and $\vec{k} \| \vec{E} \times \vec{B}$
  • C
    $\vec{X} \| \vec{B}$ and $\vec{k} \| \vec{E} \times \vec{B}$
  • D
    $\vec{X} \| \vec{E}$ and $\vec{k} \| \vec{B} \times \vec{E}$
Solution:
1992 Upvotes Verified Answer
The correct answer is:
$\vec{X} \| \vec{B}$ and $\vec{k} \| \vec{E} \times \vec{B}$
Direction of polarization is parallel to magnetic field,
$\therefore \quad \overrightarrow{\mathrm{X}} \| \overrightarrow{\mathrm{B}}$
and direction of wave propagation is parallel to $\overrightarrow{\mathrm{E}} \times \overrightarrow{\mathrm{B}}$
$\therefore \quad \overrightarrow{\mathrm{K}} \| \overrightarrow{\mathrm{E}} \times \overrightarrow{\mathrm{B}}$

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