TwiddleLab / Courses / Physics
Waves and Sound
Lessons
- A Wave Moves, the Rope Doesn't (5 min): A wave is a disturbance that travels: the hump moves, the rope stays where it is.
- Frequency, Wavelength, Speed (7 min): Frequency f: how many crests pass a point each second, in hertz (Hz). The period T = 1/f is the time for one.
- Sound Is a Pressure Wave (7 min): Sound is a pressure wave: squeezes and stretches of air that travel, while each bit of air only jiggles back and forth.
- Pitch and Loudness (7 min): Pitch is set by frequency: more waves per second sound higher.
- Echoes: Sonar and Ultrasound (7 min): Waves reflect: sound bounces back from a wall, a moth or the sea floor as an echo.
- Waves Add Up: Interference (7 min): Superposition: where waves overlap, their heights add. Afterwards each one carries on unchanged.
- Standing Waves: Why Strings Have Notes (7 min): A string fixed at both ends can only hold standing waves with a whole number of loops: λ = 2L / n.
- Resonance: Pushing at the Right Time (7 min): Everything that can swing or vibrate has a natural frequency: its own rhythm when left alone.
- The Doppler Effect (7 min): A moving source squeezes its crests together in front and spreads them out behind: the Doppler effect.
- Project: Build an Instrument (8 min): On strings of the same tension, frequency goes as 1 / length: 2/3 of the length plays 3/2 of the frequency.
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