A plane electromagnetic wave of frequency 50 MHz travels in free space along the positive x- direction. At a particular point in space and time, E = 6.3j V/m The corresponding magnetic field B at that point will be: (a) 18.9 × 10 - 8 k T (b) 2.1 × 10 - 8 k T (c) 6.3 × 10 - 8 k T (d) 18.9 × 108 k T

Answer: (b). B = E/c = 6.33×10⁸ = 2.1×10⁻⁸ T (frequency is not needed). Travel along +x, E along j: j× k = i, so B is along k. So the answer is (b) 2.1×10⁻⁸ k T.

A plane electromagnetic wave of frequency 50 MHz travels in free… | JEE Main 2019 (9 Jan, Shift 1)

Q64JEE Main 2019 · 9 JAN · SHIFT 1Easy

Nature of EM Waves & Wave Equation

A plane electromagnetic wave of frequency 50 MHz travels in free space along the positive x- direction. At a particular point in space and time, $\vec{E} = 6.3\hat{j}\text{ V/m}$ The corresponding magnetic field $\vec{B}$ at that point will be:

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Answer: (b)

$B = \dfrac{E}{c} = \dfrac{6.3}{3\times10^{8}} = 2.1\times10^{-8}\text{ T}$ (frequency is not needed).
Travel along $+x$ , $\vec E$ along $\hat j$ : $\hat j\times\hat k = \hat i$ , so $\vec B$ is along $\hat k$ .
So the answer is (b) $2.1\times10^{-8}\,\hat k$ T.

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Nature of EM Waves & Wave Equation question from JEE Main 2019 (9 Jan, Shift 1)

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