Q 12-08-049JEE MainJEE Main 2025 (29 Jan, Shift 2)Easy
A plane electromagnetic wave propagates along the $+x$ direction in free space. The components of the electric field $\vec E$ and magnetic field $\vec B$ vectors associated with the wave in the Cartesian frame are
Answer: (B) $E_y,\ B_z$
EM waves are transverse: $\vec E$ and $\vec B$ are both perpendicular to $\hat x$, so neither can have an $x$-component. Also $\vec E\times\vec B$ must point along $+x$: $\hat j\times\hat k = \hat i$, so $E_y$ with $B_z$.
(Option 3, $E_z$ with $B_y$, is transverse too, but $\hat k\times\hat j = -\hat i$ would send the wave along $-x$.)
Solution by Sreeraj P, M.Sc Physics