An unusual-looking device. Two DC motors on the end of plastic arms are connected to a center piece with a 3-color LED strobe light and a dials and buttons to control it. A length of string is connected between the two motors.
This can be used to demonstrate the appearance of standing waves in a string. Specifically, the sort of standing waves that are formed by the spinning of a string. This can also be used to show how strobe lights can shed light on rapidly-changing-but-periodic systems.
This demo is capable of showing anywhere from a half wavelength to two wavelengths by adjusting the motor speed and motor separation in 'Manual' mode. If the 'Demo' mode is selected, it will put on an impressive light display and go through varying strobe light frequencies and motor speeds.