When source is linear, the wavefront is

Options

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

Answer

To solve the question, we need to analyze the characteristics of wavefronts produced by different types of sources.

### Step-by-Step Solution:

1. **Understanding Wavefronts**: A wavefront is defined as the surface over which an oscillation has a constant phase. In simpler terms, it is the imaginary surface that connects all points that are in the same phase of the wave.

2. **Types of Sources**: There are two main types of sources that produce wavefronts:
- **Point Source**: A point source emits waves uniformly in all directions, forming spherical wavefronts.
- **Linear Source**: A linear source emits waves along a line, which can be visualized as a series of point sources aligned in a straight line.

3. **Characteristics of a Linear Source**:
- A linear source, such as a tube light, emits light in a cylindrical manner.
- As the light travels away from the linear source, it forms cylindrical wavefronts.

4. **Cylindrical Wavefront Formation**:
- At a distance \( x \) from the linear source, the wavefront is cylindrical because every point on the wavefront is equidistant from the source, and thus, all points are in the same phase.
- The radius of the cylinder at any point is equal to the distance from the source, and the wavefront expands outward in a cylindrical shape.

5. **Conclusion**: Therefore, when the source is linear, the wavefront produced is cylindrical.

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

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