Transverse and longitudinal waves – how the particles move
PhysicsOscillations & WavesAges 16–17
Use it with your class: students open it from a link or a QR code, with no account needed.
Next in Oscillations & Waves
A row of particles in a medium is set oscillating by a source at the left end; switch between a transverse wave (particles oscillate perpendicular to the direction of travel) and a longitudinal wave (particles oscillate along the direction of travel, forming compressions and rarefactions). One particle is marked in red to show that it only oscillates about its equilibrium position; the wavelength λ = v/f, the period T and the particle's displacement graph update instantly as f, A and v change.
Lesson: Describing waves; transverse and longitudinal waves; wavelength, frequency and wave speed
What it shows
A mechanical wave is an oscillation that travels through a medium. The particles of the medium only oscillate about their equilibrium positions; what travels is the state of oscillation (the phase) and energy. In a transverse wave the particles move perpendicular to the direction of travel, and in a longitudinal wave they move along it, forming compressions and rarefactions. The period is T = 1/f, and in one period the wave advances one wavelength, so λ = vT = v/f. A particle a distance x from the source starts oscillating x/v later than the source.
How to use
Start with Transverse wave and follow the red particle: it moves up and down about its equilibrium position (dashed line) but never travels with the wave. The bracket between two neighbouring crests shows λ; compare it with v/f. Switch to Longitudinal wave and locate the compressions and rarefactions. Change Frequency, Amplitude and Wave speed, and tap another particle to follow it and compare its displacement graph.
Parameters you can change
- Type of wave Transverse wave, Longitudinal wave
- Frequency 0.2–2 Hz
- Amplitude 0.5–3 cm
- Wave speed 5–40 cm/s
Questions to explore
- Does the red particle move to the right along with the wave? What does the wave actually carry?
- If the wave speed stays the same and the frequency doubles, how does the wavelength change?
- Why can sound travel through air only as a longitudinal wave, not a transverse one?
