Light waves travel in vacuum along the y-axis. Which of the following may represent the wave front?

Options

A. x=constant
B. y=constant
C. z=constant
D. x+y+z=constant

Answer

To solve the question, we need to understand the concept of wave fronts and how they relate to the direction of wave propagation.

### Step-by-Step Solution:

1. **Understanding Wave Fronts**:
- A wave front is defined as the surface over which an oscillation has a constant phase. In simpler terms, it is the surface connecting all points that are in the same phase of the wave.

2. **Direction of Wave Propagation**:
- In this case, the light waves are traveling along the y-axis. This means that the direction of wave propagation is vertical, moving up and down along the y-axis.

3. **Perpendicularity of Wave Fronts**:
- Wave fronts are always perpendicular to the direction of wave propagation. Therefore, since the light is traveling along the y-axis, the wave fronts must be perpendicular to this direction.

4. **Identifying the Plane**:
- If the light is moving along the y-axis, the wave fronts will be in planes that are perpendicular to the y-axis. This means that the wave fronts will lie in the xz-plane (where y is constant).

5. **Mathematical Representation**:
- We can represent the wave front mathematically by the equation \( y = C \), where C is a constant. This indicates that at any given wave front, the y-coordinate remains constant while the x and z coordinates can vary.

6. **Conclusion**:
- Therefore, the correct representation of the wave front for light waves traveling along the y-axis is a plane defined by the equation \( y = C \), which lies in the xz-plane.

### Final Answer:
The correct option is the one that represents the wave front as a plane perpendicular to the y-axis.

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