Only the wavelengths that fit can ring

Science · Waves, Light & Sound · ages 18-20

Name ______________________ Date ____________

The fundamental is 110 hertz. What is the third harmonic?
- 220 hertz
- 330 hertz
- 440 hertz
What can a string fixed at both ends do?
- Ring only fitting wavelengths with end nodes
- Ring any wavelength at will
- Stay silent at every frequency
A pipe closed at one end supports every harmonic.
Circle one: True False
An open pipe has a fundamental of 110 hertz. What is its fourth harmonic in hertz?
Answer: ______________
Why does a closed pipe miss the even harmonics?
- Even harmonics travel too fast
- Closed pipes lack air columns
- Closed end forces a node while open forces an antinode
In a standing wave, what are nodes and antinodes?
- Still points and widest swinging points
- Loud and soft instruments
- Open and closed ends only
A violin and a flute play the same note but sound different. Why?
- Their fundamentals differ in pitch
- One of them breaks physics
- Their harmonic mixes differ
Why does a closed pipe sound an octave lower than the same length open?
- Its air column is colder
- Its fundamental fits a longer wave, half the frequency
- It skips its fundamental

Answer key

For grown-ups. Fold this page away before handing over the rest.

330 hertz · Multiply the fundamental by the harmonic number.
Ring only fitting wavelengths with end nodes · Fixed ends force still nodes there, which admits only fits.
False · Its end conditions admit only the odd harmonics.
440 · Open pipes keep every multiple, so 4 times 110 is 440.
Closed end forces a node while open forces an antinode · Even fits would break one of the two end rules.
Still points and widest swinging points · Nodes rest while antinodes swing widest between them.
Their harmonic mixes differ · Timbre is the harmonic recipe, and each instrument blends its own.
Its fundamental fits a longer wave, half the frequency · The quarter wave fit is twice as long as the half wave fit.