Doppler Effect Demonstration

Homer Ren

The Doppler shift is a visual and auditory illustration of how the frequency of a wave changes when the source of the wave is moving relative to an observer. The purpose of this demonstration is to help people understand the Doppler effect and how it applies to different situations, such as the sound of a siren on a moving ambulance, the frequency of light from distant stars, or the speed of a moving object. By observing the shift in frequency and wavelength of waves, the demonstration can help people understand the underlying physical principles that govern the behavior of waves in motion. The demonstration can be conducted using a variety of tools and techniques, such as sound waves, light waves, or even water waves, and can be used to teach students and non-experts about the Doppler effect in a fun and interactive way.



Content Show this video. (at 5:55-6:30 and 6:51-7:18)

In the first part the sound source is moving. In the second part the source stays stationary. 

This very common phenomenon can be often ignored but the physic behind this is actually Doppler Effect!  This simulation can show what is wave very intuitively. This tone generator generates sound with different frequencies. It can give students a sense of the pitches.  A tone generator on phone so that you can swing it around a frequency dectector to simulate the ambulance approaching and leaving. 


The frequecy detector used in this demo. Setups before recording the sound: 

1. Set the recording channel to Mono. 

2. Press Ctrl+P go to the preferences page and select Spectrograms under Tracks tag. Set up as below: 

3. The recording interface. 

4. As the phone is swung steadily back and forth about the computer can get the similar graph as below:

The frequency goes down as the phone leaves away from the computer and goes up as approaching. 

Can also do this by sticking the phone on a remote control car. But this time the frequency just goes up and down once. 
Use the animation in the slides to illustrate the principle of Doppler Effect. Can follow the script in the sclides

Let students solve the problem on the worksheet which is handed out before class. 

Give the table of the formulas of all the circumstances for further interst. 

Show students 2-D Doppler Effect by just giving them a glimpse on it. Simulation of Doppler Effect to play around. 
At last can talk about the application of the Doppler Effect. 


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