Physics (university) · Part 05
Oscillations and waves
Back-and-forth motion, springs, pendulums, sound and wave behaviour.
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- Simple harmonic motionBack-and-forth motion where the restoring force is proportional to the displacement and points back to the middle.
- Period and frequencyPeriod is the time for one full cycle. Frequency is cycles per second, in hertz. They are inverses: f = 1/T.
- Mass on a springA spring pulls with force F = -kx. The period depends on mass and stiffness, T = 2 pi sqrt(m/k), not on amplitude.
- Simple pendulumA mass on a string swinging through small angles. Its period T = 2 pi sqrt(L/g) depends on length, not mass.
- ResonanceA big response when a driving force matches an object's natural frequency. Damping limits how big it gets.
- Wave speedFor any wave, speed equals frequency times wavelength: v = f lambda.
- Transverse and longitudinal wavesIn a transverse wave the medium moves at right angles to the wave direction. In a longitudinal wave it moves along the direction.
- SuperpositionWhen waves meet, their displacements add. After meeting they carry on unchanged.
- Standing wavesA fixed pattern of nodes and antinodes made by two waves moving in opposite directions. Only certain frequencies fit.
- Doppler effectThe pitch you hear changes when source and listener move toward or away from each other.
- Sound intensity levelLoudness measured in decibels (dB), a log scale where +10 dB means ten times the intensity.