The velocity of electromagnetic wave is parallel to

Options

A. `B xx E`
B. `E xx B`
C. E
D. B

Answer

To solve the question regarding the direction of the velocity of an electromagnetic wave, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Components of Electromagnetic Waves**:
- Electromagnetic waves consist of oscillating electric fields (E) and magnetic fields (B).
- The electric field and magnetic field are perpendicular to each other and to the direction of wave propagation.

2. **Define the Directions of E and B**:
- Let's assume the electric field (E) is oscillating in the y-direction.
- The magnetic field (B) is oscillating in the z-direction.

3. **Use the Right-Hand Rule**:
- To find the direction of the wave's velocity (v), we can use the right-hand rule.
- Point your fingers in the direction of the electric field (E), curl them towards the direction of the magnetic field (B), and your thumb will point in the direction of the wave's velocity (v).

4. **Determine the Direction of Velocity**:
- According to our assumption, if E is in the y-direction and B is in the z-direction, then by the right-hand rule, the velocity vector (v) will be in the x-direction.

5. **Conclusion**:
- Therefore, the velocity of the electromagnetic wave is parallel to the cross product of the electric field and magnetic field vectors, which is represented as \( \mathbf{v} \parallel \mathbf{E} \times \mathbf{B} \).
- Hence, the correct answer is that the velocity of the electromagnetic wave is parallel to \( \mathbf{E} \times \mathbf{B} \).

### Final Answer:
The velocity of the electromagnetic wave is parallel to \( \mathbf{E} \times \mathbf{B} \).

---