This Demonstration simulates the movement of "atoms" vibrating around a pulsating source. These might, for example, represent radial longitudinal oscillations of sound waves. The source oscillates sinusoidally at a chosen frequency and then movement of the seven circles of atoms follows the pulsation of the blue ball with an increasing phase delay. During one cycle, the pulsation occurs at a chosen frequency (1 to 10 cycles/sec) with increasing and decreasing sinusoidal amplitude. The volume of the blue ball and the position of the outer atoms may be read on the upper graph.
It is also possible to change the inertia of the medium by increasing the mass of the atoms; this changes the phase of the seven gray circles. The upper graph shows the relationship between inertia and phase. If the phase delay is slight, the frequencies of all the vibrating atoms remain essentially unchanged.
Their amplitudes may change if the damping factor is increased. The extreme right position of the slider results in zero amplitude (no movement at all) of the outer ring.