PARTICLES OSCILLATE. THE DISTURBANCE TRAVELS.
Transverse & longitudinal waves.
Follow one particle. Freeze the whole medium. See how the two displacement graphs are built.
Watch the particles
Transverse waveClick a particle · drag to pan · scroll or pinch to zoom
Selected particle
● Medium particles● Selected particle○ Equilibrium position
Displacement–distance
A snapshot of every particle at the current time.
Each plotted point uses the particle’s equilibrium position x₀. It is not a picture of the medium’s shape in longitudinal mode.
Displacement–time
One selected particle, observed as time passes.
Solid: elapsed time. Dashed: the same particle’s predicted motion. Selecting another particle updates this whole graph.
Two graphs. Two different questions.
Where are the particles now?
Pause the animation. Measure each particle’s displacement from its own equilibrium position. Plot those displacements against x₀ to make the displacement–distance graph. One spatial repeat is the wavelength λ.
What happens to one particle?
Select a particle and watch its ruler. Plot its displacement as time passes to make the displacement–time graph. One complete oscillation takes a period T; the frequency is f = 1/T.
In a transverse wave, positive displacement is upwards. In a longitudinal wave, positive displacement is to the right. The wave travels right in both modes; the particles oscillate about fixed equilibrium positions.
About the model and scales
This is an ideal sinusoidal travelling wave in a uniform, undamped medium. The displayed particles are samples of a continuous medium. Longitudinal rows have the same motion and represent neighbouring parts of that medium. The amplitude range is small enough to keep the particles in order, including at the shortest wavelength.
You can change frequency and wavelength independently, so wave speed changes according to v = fλ. This model does not fix one particular material’s wave speed. Changing a wave setting resets time. The displacement ruler has its own labelled scale; transverse displacement is magnified in the medium view for readability.
Explore particle motion and wave graphs
Switch between transverse and longitudinal waves, select any particle, and compare its displacement ruler with displacement–time and displacement–distance graphs. Adjust amplitude, frequency and wavelength, freeze or step the motion, and zoom or pan through the medium.
Supports wave fundamentals in IB Physics and A Level Physics, with particle-motion and graph-reading practice for AP Physics. The particles oscillate about fixed equilibrium positions while the disturbance travels. Frequency and wavelength are independently adjustable, so the wave speed changes according to v = fλ.