Ncert Exercises & Solutions

An electromagnetic wave travels in a vacuum along the

$z$ -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: $B=\dfrac{1}{c}\left(E_1 \hat{i}-E_2 \hat{j}\right) \cos (k z-\omega t)$
(b)	The associated magnetic field is given as: $E=\dfrac{1}{c}\left(E_1 \hat{i}-E_2 \hat{j}\right) \cos (k z-\omega t)$
(c)	The given electromagnetic field is circularly polarised.
(d)	The given electromagnetic wave is plane polarised.

Choose the correct options:
1. (b), (c)
2. (a), (c)
3. (a), (d)
4. (c), (d)

Given,

$\vec{E}=(E_2\hat{i}+E_2\hat{j})cos(kz-\omega t)$
We know that,

$\vec{B}=\frac{\vec{E}}{c}$

$\Rightarrow \vec{B}= \frac{E_1 \hat{i}+E_2\hat{j}}{c} cos(kz-\omega t)$
Also

$\vec{E}$ &

$\vec{B}$ are perpendicular to each other and the propagation of em-waves is perpendicular to

$\vec{E}$ as well as

$\vec{B},$ so the given em-wave is plane polarised.