Wave-Wave Interactions: Wave Interference: Beats

What is are Beats ? What causes interference in the form beats?

  The formation of beats can occurs whenever two overlapping waves are traveling in the same direction but have slightly different frequencies. Since the wavlengths are different, the phase difference between the two waves will vary as one moves along the wave. There will be places where the two waves are in phase and add constructively, as well as places where the waves are out of phase and add destructively. The wave resulting from this interference will have an amplitude that varies in space, as the interference between the two original waves oscillates between constructive and destructive.

Experiment with this simulation to develop a more thorough understanding of the beats. Start by setting the same amplitude and wavenumber for the two original waves (blue and green plots). Press the CLAW icon to see the sum of these two waves in the bottom red plot. See what happens if you shift one wave with respect to the other by moving the phase slider. Now slightly change the wavenumber of one of the waves. What happens? What happens as the wavenumber difference between the two waves increases?

Use the above simulation to answer the following questions?