Easy MCQ +4 / -1 PYQ · JEE Mains 2020

The magnetic field of a plane electromagnetic wave is
$$\overrightarrow B = 3 \times {10^{ - 8}}\sin \left[ {200\pi \left( {y + ct} \right)} \right]\widehat i$$ T
where c = 3 $\times$ 108 ms–1 is the speed of light. The corresponding electric field is :

  1. A $$\overrightarrow E = - {10^{ - 6}}\sin \left[ {200\pi \left( {y + ct} \right)} \right]\widehat k$$ V/m
  2. B $$\overrightarrow E = - 9\sin \left[ {200\pi \left( {y + ct} \right)} \right]\widehat k$$ V/m Correct answer
  3. C $$\overrightarrow E = 9\sin \left[ {200\pi \left( {y + ct} \right)} \right]\widehat k$$ V/m
  4. D $$\overrightarrow E = 3 \times {10^{ - 8}}\sin \left[ {200\pi \left( {y + ct} \right)} \right]\widehat k$$

Solution

Given, $$\overrightarrow B = 3 \times {10^{ - 8}}\sin \left[ {200\pi \left( {y + ct} \right)} \right]\widehat i$$ T <br><br>$\therefore$ E<sub>0</sub> = CB<sub>0</sub> <br><br>= 3 × 10<sup>8</sup> × 3 × 10<sup>–8</sup> = 9 V/m <br><br>We know, $\left( {\overrightarrow E \times \overrightarrow B } \right)||\overrightarrow C$ <br><br>And here $\widehat B = \widehat i\&amp; \widehat C = - \widehat j$ <br><br>$\therefore$ $\widehat E = - \widehat k$ <br><br>So, $$\overrightarrow E = - 9\sin \left[ {200\pi \left( {y + ct} \right)} \right]\widehat k$$ V/m

About this question

Subject: Physics · Chapter: Electromagnetic Waves · Topic: Maxwell's Equations

This question is part of PrepWiser's free JEE Main question bank. 109 more solved questions on Electromagnetic Waves are available — start with the harder ones if your accuracy is >70%.

Drill 25 more like these. Every day. Free.

PrepWiser turns these solved questions into a daily practice loop. Chapter-wise drills, full mocks, AI doubt chat. No auto-renew.

Start free →