Question

An electromagnetic wave is propagating along x-axis. At any instant, the phase difference between the electric field ($\vec{E}$) and magnetic field ($\vec{B}$) is

• A. zero
• B. $\frac{\pi}{4}$
• C. $\frac{\pi}{2}$
• D. $\pi$

Hint:

In EM waves, $E$ and $B$ are always in phase but perpendicular in direction.

Answer 1

The Correct Option is A

Concept: In an electromagnetic wave, the electric field $\vec{E}$ and magnetic field $\vec{B}$ oscillate in phase.

Step 1: Nature of EM wave For a plane EM wave: \[ \vec{E} = E_0 \sin(kx - \omega t), \quad \vec{B} = B_0 \sin(kx - \omega t) \]

Step 2: Phase comparison Both $E$ and $B$ have the same phase term $(kx - \omega t)$.

Step 3: Conclusion Hence phase difference: \[ \Delta \phi = 0 \] Final Answer: \[ \boxed{(A)} \]