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) a high -pressure pulse starts travelling up the pipe, if the other end of the pipe is open.
B. (b) a low -pressure pulse starts travelling up the pipe, if the other end of the pipe is open.
C. ( c ) a low -pressure pulse starts travelling up the pipe, if the other end of the pipe is closed.
D. (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 the behavior of the air pulse when it reaches the end of the pipe, considering whether the end of the pipe is open or closed.

### Step-by-Step Solution:

1. **Understanding the Situation**:
- A person blows into the open end of a long pipe, creating a high-pressure pulse of air that travels down the pipe.

2. **Analyzing the End of the Pipe**:
- We need to consider two scenarios:
- **Scenario 1**: The other end of the pipe is open.
- **Scenario 2**: The other end of the pipe is closed.

3. **Scenario 1 - Open End**:
- When the high-pressure pulse reaches the open end of the pipe, it encounters an open atmosphere.
- The high-pressure air will dissipate into the lower pressure of the atmosphere, resulting in a low-pressure region being created in the pipe.
- Therefore, a low-pressure pulse will start traveling back up the pipe.

4. **Scenario 2 - Closed End**:
- If the other end of the pipe is closed, the high-pressure pulse cannot escape.
- Instead, it will reflect back towards the source.
- Since there is no place for the high-pressure air to go, it remains in the pipe, and we will still have a high-pressure pulse traveling back up the pipe.

5. **Conclusion**:
- If the other end of the pipe is open, a low-pressure pulse starts traveling up the pipe (Option 2).
- If the other end of the pipe is closed, a high-pressure pulse starts traveling up the pipe (Option 4).
- Thus, the correct answers are Option 2 and Option 4.

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