H2-41
Demonstrates Doppler effect

An electronic device making a loud squeal is turned on and placed inside a foam ball. The ball is then zipped inside a cloth cover hooked to the end of a cord, and whirled about the instructor's head or carefully tossed from person to person. The Doppler effect can easily be heard throughout even a large room.
Engagement Suggestion:
• Challenge students to describe other circumstances where they have heard this phenomenon
Background:

This is a classic illustration of the Doppler Effect. When a wave source is in motion, the wavelength of the emitted waves is observed to change by an observer along its direction of motion.

It can be useful to present this in conjunction with an animation or simulation, to illustrate the effect visually; see the relevant page of our Directory of Simulations.
H2