The wavefronts of light coming from a distant source of unknown shape are nearly

Options

A. Plane
B. elliptical
C. cylindrical
D. spherical.

Answer

To solve the question regarding the wavefronts of light coming from a distant source of unknown shape, we can follow these steps:

### 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 represents the points in space that are reached by the wave at the same time.

2. **Characteristics of Distant Light Sources**:
- When light comes from a distant source, the light rays can be considered to be parallel due to the large distance. This is a key concept in wave optics.

3. **Types of Wavefronts**:
- Wavefronts can take various shapes depending on the source:
- **Spherical Wavefronts**: Emanate from a point source.
- **Cylindrical Wavefronts**: Emanate from a line source.
- **Planar Wavefronts**: Emanate from a very large source or a source at a great distance.

4. **Application to the Question**:
- Since the question states that the source is distant, regardless of its actual shape (whether it is spherical, cylindrical, or elliptical), the wavefronts will appear to be planar when observed from a significant distance.

5. **Conclusion**:
- Therefore, the wavefronts of light coming from a distant source of unknown shape can be considered as nearly planar.

### Final Answer:
The wavefronts of light coming from a distant source of unknown shape are nearly **planar**.

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