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Electromagnetic Waves — Physics STD 12 Science — Question

Gujarat BoardEnglish MediumSTD 12 SciencePhysicsElectromagnetic Waves1 Mark
MCQ
Choose the correct answer from alternatives given. If $\overrightarrow{\text{E}}$ and $\overrightarrow{\text{B}}$ represent electric and magnetic field vectors of an electromagnetic wave, the direction of propagation of the wave is along.
  • A
    $\overrightarrow{\text{B}}\times\overrightarrow{\text{E}}$
  • B
    $\overrightarrow{\text{B}}$
  • C
    $\overrightarrow{\text{E}}$
  • ✓
    $\overrightarrow{\text{E}}\times\overrightarrow{\text{B}}$
✓

Answer

Correct option: D.
$\overrightarrow{\text{E}}\times\overrightarrow{\text{B}}$

Electromagnet waves have electric field as well as magnetic field which are perpendicular to each other and the electromagnetic waves propagate in a direction
which is perpendicular to both the fields.
Thus the propagation vector of $EM$ waves $\overrightarrow{\text{k}}=\overrightarrow{\text{E}}\times\overrightarrow{\text{B}}$

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