A person blows into open-end of a long pipe. As a result, a high-pressure pulse of air travels down the pipe. When this pulse reaches the other end of the pipe.
Phase change of from denser medium and no phase charge from a rarer medium. For sound, the close end of the pipe is a rarer medium and open end is a denser medium.
When a high-pressure pulse travels down a pipe and reaches the end, its behavior depends on whether the end is open or closed. This is due to the reflection of sound waves at boundaries.
Key Concept: At a closed end, the air cannot move, so the displacement is zero. This results in a pressure antinode (maximum pressure change). The reflected pulse has the same phase as the incident pulse for pressure. Therefore, a high-pressure pulse reflects as a high-pressure pulse.
At an open end, the air can move freely, so the pressure is fixed (atmospheric pressure), creating a pressure node (zero pressure change). The reflected pulse has the opposite phase for pressure. Therefore, a high-pressure pulse reflects as a low-pressure pulse.
Step-by-step reasoning:
Step 1: Identify the incident pulse: high-pressure (compression).
Step 2: For a closed end: Reflection occurs with no phase change for pressure. So, high-pressure reflects as high-pressure.
Step 3: For an open end: Reflection occurs with a phase change of 180° for pressure. So, high-pressure reflects as low-pressure (rarefaction).
Step 4: The reflected pulse travels back up the pipe.
Thus, the correct statements are:
Related Topics:
Reflection of sound waves at boundaries, pressure nodes and antinodes, and wave behavior in pipes are key concepts here. This is fundamental in understanding standing waves in organ pipes and other acoustic systems.
Formulae:
The phase change upon reflection can be summarized:
For displacement waves:
For pressure waves (which are 90° out of phase with displacement):