This animation shows a traveling wave packet, representing the real part of the wave function of a free particle. The envelope of the wave packet moves with the group velocity. Individual waves within the envelope move with the phase velocity.
The program recognizes the following commands:
| S | Stop animation. Press any key to resume animation. |
| V | Velocity demonstration. Displays two vertical lines. One line moves with the speed of the group velocity. The other line moves with the speed of the phase velocity. Press V again to remove the two vertical lines. |
| Q | Quit program. |
| ? | Help. These commands are listed. |