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Electromagnetic Waves — Physics STD 12 Science — Question

Gujarat BoardEnglish MediumSTD 12 SciencePhysicsElectromagnetic Waves1 Mark
MCQ
An electromagnetic wave going through vacuum is described by $\text{E}=\text{E}_0\sin(\text{kx}-\omega\text{t}),\text{ B}=\text{B}_0\sin(\text{kx}-\omega\text{t})$ Then:
  • ✓
    $\text{E}_0\text{k}=\text{B}_0\omega$
  • B
    $\text{E}_0\text{B}_0=\omega\text{k}$
  • C
    $\text{E}_0\omega=\text{B}_0\text{k}$
  • D
    None of these.
✓

Answer

Correct option: A.
$\text{E}_0\text{k}=\text{B}_0\omega$

The relation between $E _0$ and $B _0$ id given by $\frac{\text{E}_0}{\text{B}_0}=\text{c}\ ....(\text{i})$
Here, $c =$ Speed of the electromagnetic wave,
The relation between $\omega ($the angular frequency$)$ and $k\ ($wave number$),$
$\frac{\omega}{\text{k}}=\text{c}\ ...(\text{ii})$
Therefore, from $(i)$ and $(ii),$ we get
$\frac{\text{E}_0}{\text{B}_0}=\frac{\omega}{\text{k}}=\text{c}$
$\text{E}_0\text{k}=\text{B}_0\omega$

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