A plane electromagnetic wave of frequency \( 20 \, \text{MHz} \) propagates in free space along \( x \)-direction. At a particular space and time, \( \vec{E} = 6.6 \, \hat{j} \, \text{V} / \text{m} \). What is \( \vec{B} \) at this point?
\( -2.2 \times 10^{-8} \, \hat{i} \, \text{T} \)
\( 2.2 \times 10^{-8} \, \hat{k} \, \text{T} \)
\( -2.2 \times 10^{-8} \, \hat{k} \, \text{T} \)
\( 2.2 \times 10^{-8} \, \hat{i} \, \text{T} \)
