Oscillations
An oscillation is a repeated motion around an equilibrium position. A swinging pendulum and a vibrating spring are familiar examples.
Period and frequency
Period and frequency describe the same repeating behaviour from two different perspectives.
f = 1 / T
Frequency f is measured in hertz (Hz), while period T is measured in seconds.
Simple harmonic motion
Simple harmonic motion is a special type of oscillation in which the restoring acceleration is proportional to the displacement from equilibrium and directed toward equilibrium.
ω = 2πf = 2π / T
Angular frequency describes how quickly the phase of an oscillation changes.
What is a wave?
A wave is a disturbance that transfers energy and information from one location to another. The particles of a medium do not necessarily travel with the wave over the same distance as the disturbance itself.
Wave speed
Wave speed connects wavelength and frequency. A wave with a larger frequency can travel at the same speed if its wavelength is correspondingly smaller.
v = fλ
v is wave speed, f is frequency, and λ is wavelength.
Sound waves
Sound is a mechanical wave produced by oscillating matter. In ordinary conditions, sound requires a material medium through which to propagate.
In air, sound travels mainly as a longitudinal pressure wave. Its speed depends on properties of the medium and its temperature.
Superposition
When waves overlap, their displacements combine. This principle allows waves to interfere constructively or destructively.
Resonance
Resonance occurs when a system is driven at or near one of its natural frequencies. Under suitable conditions, the amplitude of the resulting oscillation can become much larger.
Resonance appears in mechanical systems, sound, electrical circuits, and many other physical systems.
Standing waves
Standing waves can form when waves travelling in opposite directions interfere with one another.
Quick example
A wave has a frequency of 20 Hz and a wavelength of 3 m. What is its speed?
Using:
v = fλ
v = 20 × 3