This java applet shows the "Superposition Principle of wave"
When two or more wave moving through the same region of space,

Blue colored wave + green colored wave ==> red colored wave
    Blue wave moving toward right, (with fixed frequency f)
    Press the -/+ button: change the direction of green wave.
    two waves with same frequency and amplitude but opposite direction ==>standing wave.
    What if two wave with different amplitude?

Text Field input:
    Wavelength: enter wavelength f for blue/yellow waves,

    Frequency: enter frequency f for blue/yellow waves,
    Wave is not necessary moves with the same speed.
    We can calculate wave speed v = f*f
    Waves with two different wavelength produce beatsphenomenon. (sample GIF picture)

Change parameters with mouse
    Change phase between two waves:
      Move mouse near the center line, click mouse button and drag it left or right

    Change amplitude for each wave
      Move mouse near the highest point of wave, click mouse button and drag it up and down.

    Suspend the animation: click the mouse button.

click left mouse buttonThe animation resumes when the mouse button is released
click right mouse buttonThe animation resumes when click mouse button again

Click mouse button twice quickly to change the time scale:

You are welcomed to check out [url=]Suposition of Two Waves (with different phases,same amplitude,frequency)[/url] or [url=]Superposition of two waves (same frequency, different amplitude, phase/dir )[/url]