A light wave is travelling along `+y` axis. At a particular point on a given time, electric field vector is along `+ x` axis then the magnetic field vector is directed along:

Options

A. `- z ` axis
B. `+z ` axis
C. `-y` axis
D. `+y` axis

Explanation

To solve the problem, we need to determine the direction of the magnetic field vector when a light wave is traveling along the +y axis and the electric field vector is directed along the +x axis.

### Step-by-Step Solution:

1. **Identify the Direction of Wave Propagation**:
The light wave is traveling along the +y axis. This means the wave vector (k) is in the +y direction.

2. **Identify the Direction of the Electric Field**:
It is given that the electric field vector (E) is directed along the +x axis.

3. **Use the Right-Hand Rule**:
In electromagnetic waves, the electric field (E), magnetic field (B), and the direction of wave propagation (k) are mutually perpendicular to each other. We can use the right-hand rule to determine the direction of the magnetic field vector (B).

- Point your fingers in the direction of the electric field (E) which is along the +x axis.
- Curl your fingers in the direction of the wave propagation (k) which is along the +y axis.
- Your thumb will then point in the direction of the magnetic field (B).

4. **Determine the Direction of the Magnetic Field**:
Following the right-hand rule:
- Electric Field (E) = +x
- Wave Propagation (k) = +y
- Therefore, the Magnetic Field (B) must be in the +z direction.

5. **Conclusion**:
The magnetic field vector is directed along the +z axis.

### Final Answer:
The magnetic field vector is directed along the +z axis.

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