# Free Particle Wave Packet

A localized wave function is referred to as a wave packet. The most common wave packet has a Gaussian envelope (shape). The Schrödinger equation determines the time evolution of this wave packet. Although the square of the area of the wave packet (total probability) remains constant, the wave packet spreads in position space as shown in this model of the analytic solution. Why doesn't the wave packet change in momentum space?

## Reference:

Griffiths Quantum Mechanics p67.

### Note:

This simulation was created using the Easy Java Simulations (Ejs) modeling tool. You can modify this simulation if you have Ejs installed by right-clicking within a plot and selecting "Open Ejs Model" from the pop-up menu item. Information about Ejs is available at: < http://www.um.es/fem/Ejs/ >