The program recognizes the following commands:
|Slow. The wave starts to move at the speed of light. We follow along with the wave, viewing it in slow motion. The blue background represents air, and the red background represents glass. As the wave enters the glass, it slows down and becomes narrower (at first).
|Fast. View the wave in fast motion. Now we can see the difference between the phase velocity (the velocity of the waves inside the envelope) and the group velocity (the velocity of the envelope). We also see that the pulse broadens with time, the long-wavelength component of the pulse moving faster than the short-wavelength component of the pulse. Note that the wavelength of the wave at the front of the pulse becomes noticeably longer than the wavelength of the wave at the rear of the pulse.
|Restart. Put the pulse back in air 50 um from the glass. It sits there until either an S or F is pressed.
|Pause. Stop the animation. Press any key to resume animation.
|Help. These commands are listed.