The measurement of quantities in quantum mechanics is an important concept as it is different than the classical case.  In fact, most measurements affect the state one is measuring often with disastrous consequences (the collapse of the wave function).  The example here uses the program MeasurementApp to depict the phenomena described above.  The MeasurementApp program shows an initially localized time-dependent quantum-mechanical wave function in position and momentum space and via buttons allows the measurement of position, momentum, or energy.  The initial state and the well can be set as well as the uncertainty of which measurements in x and p will be taken.  Note that for the measurement of energy an energy eigenstate will result, but for the position and momentum measurements only an approximate eigenstate will result since, for the purposes of these simulations, we model the result of measurement of either x or p by Gaussian-shaped wave packets.  While these wave packets are not position or momentum eigenstates, they do allow a qualitative sense of what happens in the measurement process and allow us to represent the result of measurements with well-defined functions.   due to the finite precision of the measurement.

In these examples, the complex nature of the wave function is displayed in amplitude-and-phase representation where the phase, or phase angle, is depicted by color as shown below.