JEE PYQ: Electrostatics Question 3
Question 3 - 2021 (18 Mar Shift 1)
A plane electromagnetic wave of frequency 100 MHz is travelling in vacuum along the $x$-direction. At a particular point in space and time, $\vec{B} = 2.0 \times 10^{-8}\hat{k}$ T (where $\hat{k}$ is unit vector along z-direction). What is $\vec{E}$ at this point?
(1) $0.6\hat{j}$ V/m
(2) $6.0\hat{k}$ V/m
(3) $6.0\hat{j}$ V/m
(4) $0.6\hat{k}$ V/m
Show Answer
Answer: (3)
Solution
$E = Bc = 2.0 \times 10^{-8} \times 3 \times 10^8 = 6$ V/m. Direction of wave is $\hat{i}$, so $\vec{E} \times \vec{B}$ must be along $\hat{i}$: $\hat{j} \times \hat{k} = \hat{i}$. Therefore $\vec{E} = 6.0\hat{j}$ V/m.
BETA
