QM: Ground State Wave Function of Infinite Square Well

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In summary, the ground state wave function of a particle in an infinite square well is allowed because the conditions for an acceptable wave equation only require it to be smooth when the potential is finite. In the case of an infinite potential, the second derivative of the wavefunction can be infinite, which does not necessarily mean that the function is non-smooth. In practical applications, infinite potentials are only used for approximations and teaching purposes, while finite potentials have a smooth and continuous solution.
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Homework Statement



I was wondering why is the ground state wave function of a particle in an infinite square well allowed? If you drawn it out on a graph, it is one-half of a full sine wave.

But the conditions for an acceptable wave equation is one that is continuous (yes) and "smooth"(no!). How is the ground state allowed, when it "breaks" at the wells?

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The Attempt at a Solution

 
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  • #2
The wavefunction only has to be smooth when the potential is finite.

For a non-rigorous justification, take a look at the time-independent Schrodinger equation:
[tex]\frac{1}{2m}\nabla^2\psi = (E - V)\psi[/tex]
If the potential V is infinite, then the second derivative of the wavefunction can also be infinite, which corresponds to a discontinuous first derivative, a.k.a. a non-smooth function.
 
  • #3
I wouldn't worry about it too much. We know that in the real world that infinite isn't ever applicable, it's really only used for approximations and teaching. The finite square well is nicely smooth and continuous (though the transcendental equations make for a non-analytical solution that wouldn't be such a good introduction to quantum).
 

FAQ: QM: Ground State Wave Function of Infinite Square Well

1. What is the "ground state" in the context of an infinite square well?

The ground state refers to the lowest possible energy state of a system, in this case the infinite square well. It is the state in which the particle has the lowest possible energy and is the starting point for analyzing the behavior of the system.

2. How is the ground state wave function of an infinite square well determined?

The ground state wave function is determined by solving the Schrödinger equation for the infinite square well potential. This involves finding the eigenfunctions and eigenvalues of the Hamiltonian operator for the system, which represent the allowed energy states and their corresponding wave functions.

3. What is the significance of the ground state wave function in quantum mechanics?

The ground state wave function represents the most probable distribution of a particle's position and momentum in an infinite square well. It is a fundamental concept in quantum mechanics and helps to understand the behavior of particles in confined systems.

4. Can the ground state wave function be visualized or represented graphically?

Yes, the ground state wave function can be represented graphically as a probability density plot, with the x-axis representing position and the y-axis representing the probability of finding the particle at that position. It appears as a smooth curve with a peak at the center of the well and decreasing towards the edges.

5. How does the ground state wave function change for different potential wells?

The shape and behavior of the ground state wave function will vary depending on the shape and depth of the potential well. In a finite square well, for example, the wave function will have a non-zero value outside of the well, unlike the infinite square well where it is zero outside. Additionally, the number of nodes (points where the wave function crosses the x-axis) will also vary for different potential wells.

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