Interference and Beats

posted Jun 1, 2016, 12:51 PM by Tony Farley

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Interference:  Run this simulation.  Remember to download it, then go to your downloads folder and right-click on it and select Open.

Click Add Detector  and take a screenshot of the waves and the detector.

1. Click “Two Drips” and move your detector around until you find a place where the wave amplitude is really small and a place where it is really high (add multiple detectors).  This is because the two waves interfere with each other.  Sometimes they interfere and add to each other, and sometimes they subtract.  Screenshot this and explain what the detectors are showing and why.

2. Click on the Sound tab and click the Particles button to show how the air particles move when sound waves pass.  Screenshot this and explain how they move as a sound wave passes.  Look at the X's.

3. Move the Detector to a place where the wave is the largest.  Screenshot this and explain how the particles look when the wave is at its crest and how they look (density of particles) in a trough.  You may need to pause and play the simulation.

4. Press the Light tab and add a detector.  Screenshot this and explain the difference in the wave detected for red light and the wave detected for blue light.

5. Explain what interference is.


Go here to learn about beats. Beats are a special kind of interference where the two waves that are interfering are close in frequency to each other.

1.  Write down what a beat is. Include an image

2. What does the term "in phase" mean?  Include an image that illustrates this

3. When the oscilators are in phase, what is the amplitude of the blue ball?  What is the amplitude when they are out of phase?

4. Screenshot the 1+2 wave in your notes and describe what it is.

6. Explain what the 1+2 wave sounds like in "Hearing the Sum".  What is the frequency of this wave?

6. What are beats? Look here.

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