Question

In electromagnetic waves, phase difference between electric and magnetic field vectors is:

• A. $90^\circ$
• B. $135^\circ$
• C. $30^\circ$
• D. $0^\circ$

Hint:

In EM waves: $\vec{E} \perp \vec{B} \perp \vec{k}$, and $\vec{E}$ and $\vec{B}$ are always in phase.

Answer 1

The Correct Option is D

Step 1: Relation between $\vec{E$ and $\vec{B}$.} In an electromagnetic (EM) wave, the electric field vector $\vec{E}$, magnetic field vector $\vec{B}$, and the direction of propagation $\vec{k}$ are all mutually perpendicular.

Step 2: Phase relation. The $\vec{E}$ and $\vec{B}$ vectors oscillate in the same phase (they reach maximum and minimum together).

Step 3: Conclusion. Therefore, the phase difference between $\vec{E}$ and $\vec{B}$ is $0^\circ$.