Labs / Physics
Standing Waves
A string is clamped at both ends and shaken at one end. Most frequencies just wobble and wash out — but hit a harmonic and the outgoing and reflected waves superpose into a still pattern of nodes and antinodes. Sweep the frequency and tension, or grab the string to pluck it, and watch the pattern lock in.
harmonic n = 1v 12.6 m/snodes 2gain ×1.0
What to try
- Slide the frequency slowly upward. Why does the string only stand still at certain sharp values, and go quiet in between?
- Each time the pattern locks in, count the antinodes. How does that number relate to the harmonic readout?
- Tighten the tension. The wave speed climbs — so does the same frequency still land you on the same harmonic, or a different one?
- Turn on harmonic snap and sweep again. What does the string do now that it never falls between harmonics?
- Crank the damping all the way up. What happens to the height of the antinodes, and to how sharply the resonance picks out a frequency?