Plane wave front is not produced by a

Options

A. only point source of light at finite distance
B. only rectangular illuminated slit at finite distance
C. any source of light at finite distance
D. all the above

Answer

To solve the question "Plane wave front is not produced by a," we need to understand the conditions under which a plane wave front is generated.

### Step-by-Step Solution:

1. **Understanding Plane Wave Fronts**:
- A plane wave front is characterized by waves that propagate in parallel lines with equal phase. This occurs when the source of the waves is very far away, effectively at infinity.

2. **Analyzing the Options**:
- We need to evaluate the given options to determine which one does not produce a plane wave front.

3. **Option 1: Point Source at Finite Distance**:
- A point source emits waves in all directions. If the source is at a finite distance, the wave front will be spherical, not plane. Therefore, this option does not produce a plane wave front.

4. **Option 2: Rectangular Illuminated Slate at Finite Distance**:
- A rectangular illuminated slate at a finite distance will also not produce a plane wave front. The light waves will diverge from the edges, creating a non-uniform wave front.

5. **Option 3: Any Source at Finite Distance**:
- Similar to the previous options, any source that is at a finite distance will produce spherical wave fronts, not plane wave fronts.

6. **Conclusion**:
- Since all the options provided involve sources at finite distances, none of them can produce a plane wave front. Therefore, the correct answer is that a plane wave front is not produced by any of the given options.

### Final Answer:
- Plane wave front is not produced by any of the options provided (point source at finite distance, rectangular illuminated slate at finite distance, or any source at finite distance).