[Q] Sign of wavefunction in PIB

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Discussion Overview

The discussion revolves around the interpretation of the sign of the wavefunction in the context of the particle in a box (PIB) model within quantum mechanics. Participants explore the implications of positive and negative values of the wavefunction, particularly in relation to nodes and probability density.

Discussion Character

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

Main Points Raised

  • One participant questions the meaning of the sign of the wavefunction in the PIB model, seeking clarification on its significance.
  • Another participant notes that the wavefunction oscillates between positive and negative values and asks about the significance of this behavior.
  • A participant mentions that a change of sign indicates a node, where the probability density is zero.
  • One response suggests that there is no inherent meaning to the sign of the wavefunction, stating it represents a probability density amplitude that can be positive, negative, or complex.
  • Another participant seeks to understand the concept of a node and its relation to sudden changes in probability, prompting further clarification on what constitutes a "sudden" change.
  • A participant explains that at a node, the probability of finding the particle is zero, challenging the notion of this being strange and suggesting a departure from classical interpretations.
  • There is a mention that the wavefunction is exactly zero at a single point, referencing calculus to discuss the concept of a point's "length."

Areas of Agreement / Disagreement

Participants express differing views on the interpretation of the wavefunction's sign and its implications, indicating that multiple competing perspectives remain without consensus on the meaning of the sign.

Contextual Notes

Some participants highlight the need for clarity on terms such as "sudden" change and the mathematical implications of a point having zero length, which may affect the understanding of the discussion.

Alice Jin
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Dear all,

I have a question about the sign of Schrödinger equation in particle in a box.
What's the meaning of the sign (like -, +) of wavefunction in particle in a box?
Can anybody explain that?
Thank you.
 
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WHAT sign? Clarify.
 
If you draw the graph of wavefunction of PIB at any state n, the shape oscillates with - and + signs. What's the significance of it?
 
You mean that the wave function attain both positive and negative values?

What is the strange thing about that, what make you want to ask this question?
 
Why do you ask me like that?
I'm just curious about what the + and - sign of wavefunction stand for.
I know if there is a change of sign, at that point there is a node.
But basically I want to know the meaning of the sign.
 
Because sometimes one has thought a bit on why one asks the question, that one has an idea and so on.

There is no meaning about the sign of the wavefunction. The wavefunction is interprented as to the be probability density amplitude, and amplidtudes can attain both positive, negative and Complex values. So there is nothing strange that wave function have some negative and some positive values.
 
Then, how can you explain the sudden probability change in a node?
 
define "sudden" change, I don't think that is a mathematical term..
 
Ok for the state n=2 in PIB, in the middle of length(x=half lenth) there is a node which means no probability at the point. How do you explain no probability at the point?
 
  • #10
That the particle can't be found there of course. Why is that strange? Forget about classical pictures of particles and motion.

However, the wave function is only EXAKT 0 for ONE point. Now recall from calculus the "length" of a point...
 

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