JEE Main 2025 Jan 29 Shift 2, Physics Q8: Electromagnetic Waves

JEE Main2025Jan 29, Shift 2Physics

A plane electromagnetic wave propagates along the $+ x$ direction in free space. The components of the electric field, $E$ and magnetic field, $B$ vectors associated with the wave in Cartesian frame are :

A
$E_{y}, B_{x}$
B
$E_{y}, B_{z}$
C
$E_{x}, B_{y}$
D
$E_{z}, B_{y}$

Solution

For a plane EM wave in vacuum the direction of propagation, $E$ and $B$ form a right-handed orthogonal triad with $E \times B ∥ \overset{c}{^}$ , the direction of propagation.

Both $E$ and $B$ must be perpendicular to $\overset{x}{^}$ , so options (3) and (4) (which carry an $x$ -component) are eliminated.

Testing option (2): $\hat{j} \times \hat{k} = \hat{i}$ , so $E = E_{y} \hat{j}$ and $B = B_{z} \hat{k}$ give propagation along $+ \hat{i}$ , as required.

$∴$ Option (2) is correct.

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JEE Main 2025 Jan 29 Shift 2, Physics Q8: Electromagnetic Waves

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