# 9: The Particle in a Box

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• 9.1: The Particle in a One-Dimensional Box
The particle in the box model system is the simplest non-trivial application of the Schrödinger equation, but one which illustrates many of the fundamental concepts of quantum mechanics.
• 9.2: Applying the Postulates to the Particle in a 1D Box
To maintain the probabilistic interpretation of the wavefunction, the probability of a measurement of x yielding a result between -∞ and +∞ must be 1. Therefore, wavefunctions should be normalized (if possible) to ensure this requirement.
• 9.3: Particle in a Box and the Uncertainty Principle
The operators x and p are not compatible and there is no measurement that can precisely determine both x and p simultaneously. The uncertainty principle is a consequence of the wave property of matter. A wave has some finite extent in space and generally is not localized at a point. Consequently there usually is significant uncertainty in the position of a quantum particle in space.
• 9.4: Particle in a Three-Dimensional Box
The 1D particle in the box problem can be expanded to consider a particle within a 3D box for three lengths $$a$$, $$b$$, and $$c$$. When there is NO FORCE (i.e., no potential) acting on the particles inside the box. Motion and hence quantization properties of each dimension is independent of the other dimensions. This Module introduces the concept of degeneracy where multiple wavefunctions (different quantum numbers) have the same energy.
• 9.E: The Schrödinger Equation and a Particle in a Box (Exercises)
These are homework exercises to accompany Chapter 3 of McQuarrie and Simon's "Physical Chemistry: A Molecular Approach" Textmap.

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