Question

An electromagnetic wave travels in vacuum along $z$ direction: $E=\left(E_{1} \hat{ i }+E_{2} \hat{ j }\right) \cos (k z-\omega t)$. Choose the correct options from the following

• A. The associated magnetic field is given as $B =\frac{1}{c}\left(E_1 \hat{ i }+E_{2} \hat{ j }\right) \cos (k z-\omega t)$
• B. The associated magnetic field is given as $B =\frac{1}{c}\left(E \hat{ i }-E_{2} \hat{ j }\right) \cos (k z-\omega t)$
• C. The given electromagnetic field is circularly polarised
• D. The given electromagnetic wave is plane polarised

Answer 1

Answer: (A), (D)

In electromagnetic wave, the electric field vector is given as,
$E =\left(E_{1} \hat{ i }+E_{ 2 } \hat{ j }\right) \cos (k z-\omega t)$
In electromagnetic wave, the associated magnetic field vector,
$B =\frac{ E }{ C }=\frac{\left(E_{1} \hat{ i }+E_{2} \hat{ j }\right)}{ C } \cos (k z-\omega t)$
As $E$ and $B$ are perpendicular to each other and the propagation of electromagnetic wave is perpendicular to $E$ as well as $B$, so the given electromagnetic wave is plane polarised.