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Electromagnetic Waves — Physics STD 12 Science — Question

Gujarat BoardEnglish MediumSTD 12 SciencePhysicsElectromagnetic Waves2 Marks
Question
The oscillating magnetic field in a plane electromagnetic wave is given by$\text{B}_{y} = ( 8 \times 10^{-6}) sin [2\times 10 ^{11}t + 300 \pi\text{x}] T$.
  1. Calculate the wavelength of the electromagnetic wave.
  2. Write down the expression for the oscillating electric field.
✓

Answer

(HOTS)
  1. Comparing the given expression with.
$\text{B}_{y} = \text{B}_{\circ}sin\bigg(\frac{4\pi\text{t}}{T} - \frac{2\pi}{\lambda}\bigg)$
Alternate Answer
$\text{B}= \text{B}_{\circ} \sin \big(\omega\text{t} + kx\big)$
we get
$\therefore \text{k} \frac{2 \pi}{\lambda} = 300 \pi$
$\therefore \lambda = \frac{1}{150}m$ or $ \frac{2}{3} cm $ or 0.67 cm
  1. $\text{E}_{Z} = \text{E}_{\circ} sin ( 2 \times 10^{11}t + 300 \pi\text{x})\text{Vm}^{-1}$
$ = 2400 sin ( 2 \times 10^{11}t + 300 \pi\text{x})\text{Vm}^{-1}$
Alternate Answer
$\text{E}_{z} = \text{c}\times8 \times 10 ^{-6} sin ( 2 \times10^{11}t + 300 \pi\text{x})\text{Vm}^{-1}$
Award full mark if either of the second or third line expression is written without writing the first line.

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