JEE PYQ: Electromagnetic Waves Question 14
Question 14 - 2020 (03 Sep 2020 Shift 2)
The electric field of a plane electromagnetic wave propagating along the $x$ direction in vacuum is $\vec{E} = E_0 \hat{j} \cos(\omega t - kx)$. The magnetic field $\vec{B}$, at the moment $t = 0$ is:
(1) $\vec{B} = \frac{E_0}{\sqrt{\mu_0 \epsilon_0}} \cos(kx) \hat{k}$
(2) $\vec{B} = E_0 \sqrt{\mu_0 \epsilon_0} \cos(kx) \hat{j}$
(3) $\vec{B} = E_0 \sqrt{\mu_0 \epsilon_0} \cos(kx) \hat{k}$
(4) $\vec{B} = \frac{E_0}{\sqrt{\mu_0 \epsilon_0}} \cos(kx) \hat{j}$
Show Answer
Answer: (3)
Solution
$B_0 = \frac{E_0}{c} = E_0\sqrt{\mu_0 \epsilon_0}$. $\vec{B}$ is along $\hat{k}$. At $t = 0$: $\vec{B} = E_0\sqrt{\mu_0 \epsilon_0} \cos(kx) \hat{k}$.
BETA
