Demonstrations: pick one on the left. Every slider and tick box in Controls acts
live, so you can change the wavelength or gap width while the waves keep running.
Freeze a moment: pause, then step forward ⅛ of a period at a time (or back, in
the wave motion demos). The clock shows time in periods, so two steps is a quarter
period, a common exam question.
Particles P and Q: in the transverse, longitudinal, and stationary waves, drag on
the string to move P or Q. The box under Controls gives each one's displacement, which
way it moves, and their phase difference.
Ripple tank: a real wave-equation simulation, not an animation. Reflection,
refraction, diffraction, and interference all come from the same water. Light bands are
crests, dark bands are troughs. Tick Crests only for textbook-style wavefront
lines. In the interference demos, click the water to measure the path difference at a
point. In Free play, drag on the water to draw your own barriers.
Measure lets you drag a line anywhere to read off a distance in cm, such as a
wavelength. Labels & rays hides every label, ray, and line so a frame can be used
as a question. Share link copies a link that opens this demo with these settings,
and Export PNG saves the current frame.