When a sound wave is reflected from a wall the phase difference between the reflected and incident pressure wave is:

Options

A. `0`
B. `pi`
C. `pi//2`
D. `pi//4`

Explanation

To solve the problem of determining the phase difference between the reflected and incident pressure wave when a sound wave is reflected from a wall, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Reflection at a Fixed Boundary**:
- When a sound wave hits a rigid wall (fixed boundary), it reflects back. At a fixed boundary, the particles of the medium cannot move, creating a node in terms of displacement.

**Hint**: Remember that a fixed boundary behaves like a node for displacement waves.

2. **Analyzing the Incident and Reflected Waves**:
- The incident wave approaches the wall, and upon reflection, it will have a phase change. For a wave reflecting off a fixed boundary, the reflected wave undergoes a phase shift of π (180 degrees) in terms of displacement.

**Hint**: Consider how the wave behaves at the boundary and the concept of phase shift upon reflection.

3. **Phase Difference in Terms of Displacement**:
- Since the reflected wave has a phase shift of π compared to the incident wave in terms of displacement, we can denote this as:
- Phase difference (displacement) = π radians.

**Hint**: Focus on the relationship between displacement and phase shift during reflection.

4. **Understanding Pressure Waves**:
- Pressure waves are related to the displacement waves but are not the same. At a fixed boundary, while the displacement is zero (node), the pressure is at its maximum (antinode).

**Hint**: Recall that at a node for displacement, the pressure variation is maximum.

5. **Phase Difference in Terms of Pressure**:
- Since the reflected wave at the boundary has the same pressure variation as the incident wave (both are at maximum), the phase difference in terms of pressure waves is:
- Phase difference (pressure) = 0 degrees.

**Hint**: Think about how pressure waves behave at nodes and antinodes.

6. **Conclusion**:
- Therefore, the phase difference between the reflected and incident pressure wave when a sound wave is reflected from a wall is 0 degrees.

**Final Answer**: The phase difference between the reflected and incident pressure wave is 0 degrees.