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

(A) $\mathrm{E}_{\mathrm{y}}, \mathrm{B}_{\mathrm{x}}$

(C) $\mathrm{E}_{\mathrm{x}}, \mathrm{B}_{\mathrm{y}}$

(D) $\mathrm{E}_{\mathrm{z}}, \mathrm{B}_{\mathrm{y}}$

JEE Main · 2025 · 29 Jan 2025 · Shift 2 · EM Waves

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) $E_{y}, B_{z}$ ✓ Correct
(C) $E_{x}, B_{y}$
(D) $E_{z}, B_{y}$

Answer: (B)

Solution

For a plane electromagnetic wave in free space,

E

B

, and the direction of propagation form a mutually perpendicular set, related by

\overset{c}{^} = \frac{E \times B}{∣ E \times B ∣}

The wave travels along

+ x

, so

E \times B

must point along

\overset{x}{^}

. Taking

E

along

\overset{y}{^}

and

B

along

\overset{z}{^}

\overset{y}{^} \times \overset{z}{^} = \overset{x}{^}

which satisfies the requirement. The electric and magnetic field components are

E_{y}

and

B_{z}

Structure Direction of propagation diagram — Direction of propagation diagram

JEE Main · 2025 · 29 Jan 2025 · Shift 2 · Single correct option

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