This distinguishing characteristic of waves is the principle of superposition. When two waves interact their amplitudes add to produce a new wave.
You can use the program Making Waves to experiment with the superposition principle.
Start off by selecting the program called Pulse from the menu. Click on the Start button and you will see two pulses move across the screen. If you click on the Show Sum button the result of the two pulses added together in red. You can change the amplitude, wavelength, velocity and shape of each pulse.
How does each of these parameters change the sum of the pulses?
You can also change the direction of the pulse (right to left or left to right) and the phase between them.
Now return to the menu (by clicking on the Back button on the browser) and select the program called Waves. Repeat the steps for the Pulse program and observe the superposition of waves.
The following two video clips show other examples of wave superposition.
You will need to click and drag the mouse in the video window (from left to right) to play the video.
We have included some videos of slinky springs and animated strings to further illustrate the concept of superpostion. Click here for the menu.
Definitions: Constructive Interference - Waves add to increase the amplitude of the sum. Destructive Interference - Waves add to decrease the amplitude of the sum.
Use the Making Waves program to setup cases of constructive and destructive interference.