Easy MCQ +4 / -1 PYQ · JEE Mains 2021

A plane electromagnetic wave of frequency 500 MHz is travelling in vacuum along y-direction. At a particular point in space and time,
$\overrightarrow B$ = 8.0 $\times$ 10$-$8 $\widehat z$T. The value of electric field at this point is :

(speed of light = 3 $\times$ 108 ms$-$1)

$\widehat x$, $\widehat y$, $\widehat z$ are unit vectors along x, y and z directions.

  1. A 2.6 $\widehat x$ V/m
  2. B $-$24 $\widehat x$ V/m Correct answer
  3. C 24 $\widehat x$ V/m
  4. D $-$2.6 $\widehat y$ V/m

Solution

${E_0} = B.C$<br><br>${E_0} = (8 \times {10^{ - 8}}) \times (3 \times {10^8})$<br><br>$\Rightarrow {E_0} = 24$<br><br>Direction of wave travelling is in $\overrightarrow E \times \overrightarrow B$<br><br>So, $( - \widehat x) \times \widehat z = + \widehat y$<br><br>$\therefore$ $\widehat E = -24\widehat x$ V/m

About this question

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

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