Q128 / 200 · NEET 2011 (Screening) · Physics

The electric and the magnetic field, associated with an electromagnetic wave, propagating along the $+z$-axis, can be represented by

  • A
    $\left[\mathbf{E}=E_0 \hat{\mathbf{k}}, \mathbf{B}=B_0 \hat{\mathbf{i}}\right]$
  • B
    $\left[\mathbf{E}=E_0 \hat{\mathbf{j}}, \mathbf{B}=B_0 \hat{\mathbf{j}}\right]$
  • C
    $\left[\mathbf{E}=E_0 \hat{\mathbf{j}}, \mathbf{B}=B_0 \hat{\mathbf{k}}\right]$
  • Correct answer
    D
    $\left[\mathbf{E}=E_0 \hat{\mathbf{i}}, \mathbf{B}=B_0 \hat{\mathbf{j}}\right]$

Solution

$\vec{\mu}=\overrightarrow{\mathbf{E}} \times \overrightarrow{\mathbf{B}}$ $$ =E_0 \hat{\mathbf{i}}+B_0 \hat{\mathbf{j}}=E_0 B_0 \hat{\mathbf{k}} $$ $\overrightarrow{\mathbf{E}} \times \overrightarrow{\mathbf{B}}$ points in the direction of wave propagation.

Hence, the correct answer is option: 'D'.

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