Question:medium

The magnetic field of an E.M. wave is given by: \[ \vec{B} = \left( \frac{\sqrt{3}}{2} \hat{i} + \frac{1}{2} \hat{j} \right) 30 \sin \left( \omega \left( t - \frac{z}{c} \right) \right) \] The corresponding electric field in S.I. units is:

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For an electromagnetic wave, the electric and magnetic fields are perpendicular and related through the speed of light.
Updated On: Feb 2, 2026
  • \( \vec{E} = \left( \frac{1}{2} \hat{i} + \frac{\sqrt{3}}{2} \hat{j} \right) 30 c \sin \left( \omega \left( t + \frac{z}{c} \right) \right) \)
  • \( \vec{E} = \left( \frac{3}{4} \hat{i} + \frac{1}{4} \hat{j} \right) 30 c \cos \left( \omega \left( t - \frac{z}{c} \right) \right) \)
  • \( \vec{E} = \left( \frac{\sqrt{3}}{2} \hat{i} - \frac{1}{2} \hat{j} \right) 30 c \sin \left( \omega \left( t + \frac{z}{c} \right) \right) \)
  • \( \vec{E} = \left( \frac{1}{2} \hat{i} - \frac{\sqrt{3}}{2} \hat{j} \right) 30 c \sin \left( \omega \left( t - \frac{z}{c} \right) \right) \)
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The Correct Option is D

Solution and Explanation

The relationship between the magnetic field \( \vec{B} \) and electric field \( \vec{E} \) in an electromagnetic wave is described by the equation \( \vec{E} = \vec{B} \times \hat{c} \), and also by \( \vec{E} = B_0 c \), where \( c \) represents the speed of light. The given magnetic field is: \[ \vec{B} = \left( \frac{\sqrt{3}}{2} \hat{i} + \frac{1}{2} \hat{j} \right) 30 \sin \left( \omega \left( t - \frac{z}{c} \right) \right) \] The electric field \( \vec{E} \) is computed using the cross product and the relation \( \vec{E} = B_0 c \). The resultant electric field is: \[ \vec{E} = \left( \frac{1}{2} \hat{i} - \frac{\sqrt{3}}{2} \hat{j} \right) 30 c \sin \left( \omega \left( t - \frac{z}{c} \right) \right) \]
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