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Introduction When a standing wave is reected, the reected wave disturbs the same section of the medium where the original wave is. Since the two waves are in the same place at the same time, they will interfere with each other. Sometimes the net disturbance is destructive and the resulting vibration is smaller than the original wave. Sometimes the net disturbance is constructive and the resulting vibration is larger than the original wave. The combination of constructive and destructive interference create patterns that are interesting to study and model physical systems that range from the sound of an oboe to the interactions of sub-atomic particles. (The soundbox on a guitar, for example, makes the soundwave reect sooner than it would otherwise, helping to create a louder, richer sound. Even the shape is uniquely suited to bouncing the sound waves in a particular way to achieve a particular effect.) One of these patterns is called a standing wave. Standing waves have points in the medium (called nodes) that do not move. Where the wave and its reection touch is a constant. The points that move the most (those with the greatest amplitude) are called antinodes. Here are a few images of standing waves: 000000 How do waves interact with their reections? What physical properties appear which are not evident when a single wave is considered? How can these ideas he applied over a large range of physical phenomena? Materials Slinky or other large stretchy spring, a stopwatch, a meterstick Materials Slinky or other large stretchy spring, a stopwatch, a meterstick Procedure 1. Stretch the spring out to one half its full length. Secure one end by taping it to a wall or other solid structure allowing it to rest on a at bare surface (oor or table). (Another person holding the other end is also acceptable.) Move one end of the spring back and forth sending a series of waves down the spring. Adjust your frequency so that the wave looks like the rst standing wave in the images above. Estimate and record the wavelength and period of the wave. 2. Repeat step 1 for the other two standing waves shown above. Observation and Analysis Wavelength (I) Frequency (f) Velocity (I x f)