We-3 The Doppler Effect (with microwaves)
Published: Wednesday 15 March 2006 - Updated: Wednesday 30 March 2011
To demonstrate that a wave reflected from a moving object has its frequency shifted.
- Doppler Alarm unit
- Stereo Amplifier
- Steel Rule
Click on pictures to enlarge.
The Doppler alarm unit sends out a beam of microwaves. The beam reflected from a moving object (flicking a steel rule works well) is Doppler shifted. The original wave and its Doppler shifted wave are fed into a non linear device (a diode) which has as its output a component due to the difference frequency in the audible. This is amplified and clearly heard in a large lecture theatre.