A person blows into open- end of a long pipe. As a result,a high pressure pulse of air travel down the pipe. When this pulse reaches the other end of the pipe,

Options

A. a high-pressure pulse starts travelling up the pipe, if the other end of the pipe is open
B. a low-pressure pulse starts travelling up the pipe, if the other end of the pipe is open
C. a low-pressure pulse starts traveling up the pipe, if the other end of the pipe is closed.
D. a high-pressure pulse starts travelling up the pipe, if the other end of the pipe is closed.

Explanation

To solve the problem, we need to analyze what happens when a person blows into an open-ended long pipe, creating a high-pressure pulse of air. We will consider the behavior of this pulse when it reaches the other end of the pipe.

### Step-by-Step Solution:

1. **Understanding the Situation**:
- A person blows into one end of a long pipe, generating a high-pressure pulse of air.
- This pulse travels down the pipe towards the other end.

2. **Identifying the Type of Pipe**:
- The question mentions two scenarios: one where the other end of the pipe is open and another where it is closed.
- We need to analyze the behavior of the pulse in both cases.

3. **Behavior of the Pulse in an Open Pipe**:
- When the high-pressure pulse reaches the open end of the pipe, it encounters a boundary that allows air to escape.
- At an open end, the pressure pulse will undergo a phase change of π (or 180 degrees), resulting in a low-pressure pulse traveling back up the pipe.

4. **Behavior of the Pulse in a Closed Pipe**:
- If the other end of the pipe is closed, the high-pressure pulse will reflect back without any phase change.
- Thus, when the pulse reaches the closed end, it remains a high-pressure pulse and travels back up the pipe unchanged.

5. **Conclusion**:
- If the other end of the pipe is open, a low-pressure pulse starts traveling back up the pipe.
- If the other end of the pipe is closed, a high-pressure pulse continues to travel back up the pipe.

### Final Answers:
- **Option 2**: A low-pressure pulse starts traveling up the pipe if the other end of the pipe is open. (Correct)
- **Option 4**: A high-pressure pulse starts traveling up the pipe if the other end of the pipe is closed. (Correct)