Equal or larger/smaller versus larger/smaller in boundary conditions

In summary, the conversation discusses a confusion about the approach to solving two similar infinite square well problems where the potential is zero within a certain range and infinite otherwise. The speaker is unsure why the author of the solution assumes the same boundary conditions for both problems, when in the second problem, the potential is not zero at the boundary points. The speaker questions if they are missing something and asks for clarification.
  • #1
Tokki
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TL;DR Summary
I am confused about why the two seem to be approached the same in all the solutions I have seen
Hi everyone!
This is the first time I'm posting on any forum and I'm still rather unsure of how to format so I'm sorry if it seems wonky. I'll try my best to keep the important stuff consistent!
I am working on infinite square well problems, and in the example problem:
V(x) = 0 if: 0 ≤ x ≤ a
∞ : otherwise

H`ere it is obvious that one should take ψ(a)=ψ(0)=0 and solve.

In the next example problem, however, the boundaries are shown as follows:
V(x) = 0 if: -a < x < a
∞ : otherwise

Here potential is zero if x is between (-a) and (a) but not when x is equal to (-a) or (a).
However, in the solution, the author does the same thing, making ψ(-a)=ψ(a)=0
The conditions, however, do not seem to allow this.
What am I missing?
Thank you!
 
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  • #2
Tokki said:
Summary:: I am confused about why the two seem to be approached the same in all the solutions I have seen

Hi everyone!
This is the first time I'm posting on any forum and I'm still rather unsure of how to format so I'm sorry if it seems wonky. I'll try my best to keep the important stuff consistent!
I am working on infinite square well problems, and in the example problem:
V(x) = 0 if: 0 ≤ x ≤ a
∞ : otherwise

H`ere it is obvious that one should take ψ(a)=ψ(0)=0 and solve.

In the next example problem, however, the boundaries are shown as follows:
V(x) = 0 if: -a < x < a
∞ : otherwise

Here potential is zero if x is between (-a) and (a) but not when x is equal to (-a) or (a).
However, in the solution, the author does the same thing, making ψ(-a)=ψ(a)=0
The conditions, however, do not seem to allow this.
What am I missing?
Thank you!

The two problems are physically the same, whether you have ##<## or ##\le##.

Why do you think in the second case you don't have ##\psi(-a) = \psi(a) = 0##? It can't be non-zero at these points.
 
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Likes vanhees71

1. What is the difference between equal/larger versus larger in boundary conditions?

Equal or larger in boundary conditions means that the value can be equal to or larger than the specified boundary, while larger in boundary conditions means that the value must be strictly larger than the specified boundary. For example, if the boundary is set at 10, a value of 10 would be accepted for equal or larger, but not for larger.

2. How are boundary conditions used in scientific experiments?

Boundary conditions are used to define the limits of a system or experiment. They can be used to specify the starting conditions, the end conditions, or any other constraints that must be met in order for the experiment to be valid. Boundary conditions are important in ensuring the accuracy and reproducibility of scientific experiments.

3. Can boundary conditions affect the outcome of an experiment?

Yes, boundary conditions can greatly affect the outcome of an experiment. They can determine which data points are included or excluded, and can also impact the validity of the results. It is important for scientists to carefully consider and define the boundary conditions for their experiments in order to obtain accurate and meaningful results.

4. How are boundary conditions determined in scientific research?

Boundary conditions are determined through a combination of theoretical calculations and empirical data. Scientists use their knowledge of the system and previous research to determine the appropriate boundaries, and also conduct experiments to gather data and refine their understanding of the system. Boundary conditions may also be adjusted based on the results of the experiment.

5. What are some common challenges in defining boundary conditions?

One of the main challenges in defining boundary conditions is balancing realism with simplicity. The boundaries should accurately reflect the real-world conditions, but also be simple enough to allow for easy analysis and interpretation of the results. Additionally, there may be uncertainties or variations in the system that make it difficult to determine the exact boundaries. Scientists must carefully consider these factors when defining boundary conditions for their experiments.

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