Then, as you browse the listings, simply check the boxes corresponding to the demos you would like. When masked so that only one bead is visible, its shadow moves linearly up and down.
Sand collects along the nodal lines of vibrating plates.
The vibrational frequency of stretched string varies with its length. Flame height above the pipe is an analog of the wave inside. Even though they are moving in circles their projected shadows appear to move back and forth on astraight line. The shadow of a sphere mounted on the circumference of a horizontal turntable moves in a straight line. One dot moves about a circle while another moves along a diameter maintaining the same height.