Consists of an aluminum tube with a speaker, 3kHz frequency generator, and 9V battery mounted inside a large green foam ball (which has been reinforced with duct tape). A string with a rubber handle is attached to one end of the cylinder.

To demonstrate the Doppler effect.

• Doppler Ball

The unit is a self-contained apparatus containing a battery, oscillator and a speaker that is small enough to be whirled around one's head on a length of cord. Switch on and whirl around one's head at a reasonable speed and an apparent change in frequency will be observed by the class. Due to safety concerns, this demo has now been enclosed in a green foam ball in the event that the one operating the demo has poor grip or something else goes wrong.

Useful Links: The BBC provides information on “Life, the Universe and Everything” originally started by Douglas Adams and provides quite a bit of trivia on the Doppler Effect. Updated on: 06/19/13