Question

The velocity of electromagnetic wave is parallel to :-

• A. $\vec{B} \times \vec{E}$
• B. $\vec{E} \times \vec{B}$
• C. $\vec{E}$
• D. $\vec{B}$

Answer 1

The Correct Option is B

An electromagnetic wave consists of oscillating electric and magnetic fields that are perpendicular to each other and to the direction of wave propagation. To determine the direction of the velocity of the electromagnetic wave, we need to understand the following:

1. The electric field vector is represented by $\vec{E}$.
2. The magnetic field vector is represented by $\vec{B}$.
3. The direction of the wave propagation, or the velocity of the electromagnetic wave, is given by the cross product of the electric and magnetic fields, i.e., $\vec{E} \times \vec{B}$.

Let's analyze the options given in the question:

• $\vec{B} \times \vec{E}$: This represents the magnetic field crossed with the electric field, which is not the direction of wave propagation.
• $\vec{E} \times \vec{B}$: This is the correct direction for wave propagation. The velocity of an electromagnetic wave is parallel to this cross product.
• $\vec{E}$: The direction of the electric field, not the wave velocity.
• $\vec{B}$: The direction of the magnetic field, not the wave velocity.

Thus, the correct answer is $\vec{E} \times \vec{B}$ as it correctly represents the direction of the wave's velocity.