When source is linear, the wavefront is

Options

A. Spherical
B. Cylindrical
C. Circular
D. All of these

Answer

To solve the question "When the source is linear, the wavefront is:", we need to understand the concept of wavefronts and how they relate to different types of sources.

### Step-by-Step Solution:

1. **Understanding Wavefront**:
- A wavefront is defined as the locus of points that have the same phase of vibration. This means that all points on the wavefront are oscillating in unison at a given moment in time.

2. **Types of Sources**:
- Sources of waves can be categorized based on their shape. The two primary types are:
- **Point Source**: A source that emits waves uniformly in all directions, resulting in spherical wavefronts.
- **Linear Source**: A source that is extended in one dimension, such as a line of vibrating particles.

3. **Analyzing a Linear Source**:
- For a linear source, the emitted waves will not spread out in a spherical manner. Instead, the waves will propagate outward in a cylindrical shape. This is because the linear source emits waves in a plane perpendicular to its length.

4. **Conclusion**:
- Therefore, when the source is linear, the wavefront is cylindrical. This means that the wavefronts will take the shape of concentric cylinders surrounding the linear source.

### Final Answer:
When the source is linear, the wavefront is cylindrical.