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STD 12 - 8. Electromagnetic waves — NEET STD 11 Science — Question

Gujarat BoardEnglish MediumSTD 11 ScienceNEETSTD 12 - 8. Electromagnetic waves4 Marks
MCQ
A plane electromagnetic wave propagating in $\mathrm{x}$-direction is described by

$\mathrm{E}_{\mathrm{y}}=\left(200\  \mathrm{Vm}^{-1}\right) \sin \left[1.5 \times 10^7 \mathrm{t}-0.05\  \mathrm{x}\right] \text {; }$

The intensity of the wave is :(Use $\in_0=8.85 \times 10^{-12} \mathrm{C}^2 \mathrm{~N}^{-1} \mathrm{~m}^{-2}$ )

  • A
     $35.4 \ \mathrm{Wm}^{-2}$
  • ✓
    $53.1 \ \mathrm{Wm}^{-2}$
  • C
     $26.6 \ \mathrm{Wm}^{-2}$
  • D
     $106.2 \ \mathrm{Wm}^{-2}$
✓

Answer

Correct option: B.
$53.1 \ \mathrm{Wm}^{-2}$
b
$ \mathrm{I}=\frac{1}{2} \varepsilon_0 \mathrm{E}_0^2 \times \mathrm{c} $

$ \mathrm{I}=\frac{1}{2} \times 8.85 \times 10^{-12} \times 4 \times 10^4 \times 3 \times 10^8 $

$ \mathrm{I}=53.1 \mathrm{~W} / \mathrm{m}^2$

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