For point source, the wavefront is

Options

A. Cylindrical always
B. Spherical always
C. Plane always
D. May be spherical or plane, depending upon distance

Answer

To answer the question, "For a point source, the wavefront is," we will analyze the nature of wavefronts produced by a point source of waves.

### Step-by-step Solution:

1. **Understanding Wavefront**: A wavefront is defined as the locus of all points that are in the same phase of vibration. For a point source, this means that all points on the wavefront are at the same distance from the source and are oscillating in unison.

2. **Point Source Characteristics**: A point source emits waves uniformly in all directions. The nature of the wavefront depends on the distance from the source.

3. **Near the Source**: When we are close to the point source, the wavefronts are spherical. This is because the waves spread out in three-dimensional space, forming concentric spheres around the source.

4. **Far from the Source**: As we move further away from the point source, the curvature of the wavefronts becomes less pronounced. At a sufficiently large distance, the wavefronts can be approximated as flat planes. This is due to the large radius of the wavefronts compared to the distance from the source, making the curvature negligible.

5. **Conclusion**: Therefore, for a point source, the wavefronts can be described as spherical at short distances and can be approximated as plane waves at large distances.

### Final Answer:
The wavefront for a point source is spherical at short distances and can be approximated as plane at large distances.

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