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A magnetic field vector in an electromagnetic wave is represented by \(\vec{B}={B}_{0}\sin \left(2\pi \nu t-\frac{2\pi x…

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A magnetic field vector in an electromagnetic wave is represented by \(\vec{B}={B}_{0}\sin \left(2\pi \nu t-\frac{2\pi x}{\lambda }\right)\overset{^}{j}\). Its associated electric field vector is ________

[JEE Main 2026, 4 Apr (Shift 2)]

a

\(\vec{E}=-\nu \lambda {B}_{0}\sin \left(2\pi \nu t-\frac{2\pi x}{\lambda }\right)\overset{^}{k}\)

b

\(\vec{E}=-\nu \lambda {B}_{0}\sin \left(2\pi \nu t-\frac{2\pi x}{\lambda }\right)\overset{^}{i}\)

c

\(\vec{E}=v\lambda {B}_{0}\sin \left(2\pi vt-\frac{2\pi x}{\lambda }\right)\overset{^}{k}\)

d

\(\vec{E}=v\lambda {B}_{0}\sin \left(2\pi vt-\frac{2\pi x}{\lambda }\right)\overset{^}{i}\)

✓ Correct answer: a)

\(\vec{E}=-\nu \lambda {B}_{0}\sin \left(2\pi \nu t-\frac{2\pi x}{\lambda }\right)\overset{^}{k}\)

Explanation

\(\vec{B}={B}_{0}\sin \left(2\pi \nu t-\frac{2\pi x}{\lambda }\right)\overset{^}{j}\)

Since spatial term contains only \(x\) with negative sign \((\omega t-kx)\), wave propagates along \(+\overset{^}{x}\).

\(\overset{^}{E}\times \overset{^}{B}=\overset{^}{C}\)

\(\overset{^}{B}=\overset{^}{j},\overset{^}{C}=\overset{^}{j}\)

\(\overset{^}{E}\times \overset{^}{j}-\overset{^}{i}\Rightarrow \overset{^}{E}=-\overset{^}{k}\)

\({E}_{0}=c{B}_{0}=\nu \lambda {B}_{0}\)

\(\vec{E}=-\nu \lambda {B}_{0}\sin \left(2\pi \nu t-\frac{2\pi x}{\lambda }\right)\overset{^}{k}\)

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