Why is the concept of a one dimensional box used?

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Discussion Overview

The discussion revolves around the use of the concept of a one-dimensional box, often referred to as the infinite square well, in quantum mechanics. Participants explore its implications, applications, and pedagogical value, touching on its relevance in both physics and chemistry.

Discussion Character

  • Exploratory, Technical explanation, Conceptual clarification, Debate/contested

Main Points Raised

  • Some participants express confusion about the terminology, suggesting that "particle on a line segment" or "moving in one dimension" might be clearer alternatives.
  • One participant notes that the problem is not purely one-dimensional, as it assumes infinite walls in the other dimensions, leading to decoupled solutions that are plane waves.
  • Another participant emphasizes that the infinite square well, while not the most realistic potential, serves as a simple model that helps illustrate key concepts in quantum mechanics, such as discrete energy levels and the use of position and momentum operators.
  • A participant mentions the relevance of the one-dimensional box concept in chemistry, specifically in relation to polyenes.
  • One participant argues that starting with simple models, like the one-dimensional box, is a foundational approach similar to beginning classical physics with constant force in one dimension.

Areas of Agreement / Disagreement

Participants express a range of views on the clarity and utility of the one-dimensional box concept, with some agreeing on its pedagogical value while others question its terminology and realism. The discussion remains unresolved regarding the best way to frame the concept.

Contextual Notes

There are limitations in the assumptions made about dimensionality and the applicability of the model to real-world scenarios. The discussion does not resolve the complexities of the infinite square well or its implications in different contexts.

pa5tabear
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I'm not sure I know all that I should to understand it. I'm posting to try and determine if I do.

Knowing what I know, however, it seems unnecessarily confusing. Almost all students I talk to agree.

Why not just call it a particle on a line segment? Or just moving in one dimension?
 
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you assume that the walls are infinite in two other dimensions. it is not a one dimensional problem per se: two other dimensions decouple and their solutions are just plane waves, the interesting part is in the dimension where walls stand.

Quantum mechanics of one dimension is very different.
 
I've seldom heard it referred to as a "one-dimensional box." Usually it's called the infinite square well. It may not be the most realistic potential, but it's easy to solve and gives you some intuition about how quantum mechanics works (you can see the discrete energy levels, you can do simple calculations with the position and momentum operators, etc.). For a two- or three-dimensional infinite square well, you can start to discuss degeneracy too, which is essential later on. I think it's basically just a simple model that illustrates a lot of important concepts.
 
it also has some relevance for chemistry, for polyenes.
 
you have to start with something...

its like why you start classic physics with F=const in one dimension
 

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