Physics Q31 – JEE-MAIN 2026

For an electromagnetic wave propagating through vacuum,

\vec{k}

\vec{E}

and

ω

represent propagation vector, electric field and angular frequency, respectively. The magnetic field associated with this wave is represented by:

Clue 1 of 3: Fundamental Relationship

Recall the fundamental vector relationship between the electric field, magnetic field, and propagation vector in an electromagnetic wave.

🧠 Full Solution Path

Step 1: Identify Vector Relationships in EM Waves✦ Active

In an electromagnetic wave propagating in vacuum, the electric field $\vec{E}$ , magnetic field $\vec{B}$ , and propagation vector $\vec{k}$ are mutually perpendicular. The direction of propagation is given by the direction of $\vec{E} \times \vec{B}$ .

Step 2: Recall the Formula for Magnetic Field○ Expand

The magnetic field $\vec{B}$ associated with an electromagnetic wave can be expressed in terms of the electric field $\vec{E}$ and the propagation vector $\vec{k}$ as:

\vec{B} = \frac{1}{ω} (\vec{k} \times \vec{E})

Here, $ω$ is the angular frequency of the wave.

💡 Teacher's Secret Hint

Remember that the cross product order matters: $\vec{k} \times \vec{E}$ is not the same as $\vec{E} \times \vec{k}$ .

Step 3: Compare with Given Options○ Expand

Comparing the derived formula $\vec{B} = \frac{\vec{k} \times \vec{E}}{ω}$ with the given options, we find that option 2 matches this relationship exactly.

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Physics Question 31 – JEE-MAIN 2026

Clue 1 of 3: Fundamental Relationship

🧠 Full Solution Path