Stationary source                                                            Moving source

         Speed of source = speed of wave                                         Speed of source > speed of wave

Click the screen once to activate the microphone. Move it around to hear the observed frequency at different positions.

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By dragging the green source or red observer you can make them move.

1. Press "Play simulation"
2. What happens to the observed frequency (increase/decrease/same) when you:
   1. Move the observer away from the source?
   2. Move the observer toward the source?
   3. Move the source away from the observer?
   4. Move the source toward the observer?

How can you use your observations to select the correct formula from the data booklet?

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