Wave Motion Visualization

Several particles spin in place directly on the sine curve — each one's circular motion generates the curve's height at that exact point (dashed line = the projection).

The particle spinning on the circle (left) drives a piston that moves back and forth in a straight line — exactly how one air particle moves in a longitudinal sound wave. Traced over time (right), that same back-and-forth motion draws a sine curve, even though the real motion never left a straight line.

This is the same back-and-forth motion, repeated across many particles with a slight delay between neighbors — that delay is what makes the wave travel.