Time Dependent Schrodinger Equation

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Homework Help Overview

The discussion revolves around demonstrating that the wave function ##\Psi(x,t)=Asin(kx-ωt)## does not satisfy the time-dependent Schrödinger equation. The context is rooted in quantum mechanics, specifically the application of differential equations to wave functions.

Discussion Character

  • Exploratory, Assumption checking, Mathematical reasoning

Approaches and Questions Raised

  • Participants discuss substituting the wave function into the Schrödinger equation and the implications of doing so. There are attempts to simplify the problem by assuming a potential V = 0, and questions arise regarding the validity of this assumption. Some participants express uncertainty about their differential equations knowledge and seek clarification on the process of differentiation.

Discussion Status

The discussion is ongoing, with participants providing guidance on how to approach the problem, such as focusing on partial derivatives. There is acknowledgment of confusion regarding the notation used in the differentiation process. Multiple interpretations of the requirements for the wave function to satisfy the Schrödinger equation are being explored.

Contextual Notes

Participants note a lack of recent experience with differential equations and calculus, which may impact their understanding of the problem. There is also a discussion about the assumption of a zero potential and its implications for the wave function.

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Homework Statement


Show that the wave function ##\Psi(x,t)=Asin(kx-ωt)## does not satisfy the time dependent Schrödinger Equation.


Homework Equations



##-\frac{\hbar}{2m}\frac{\partial^2\psi(x,t)}{{\partial}x^2}+V(x,t)\psi(x,t)=i\hbar\frac{\partial\psi(x,t)}{{\partial}t}##

The Attempt at a Solution


So first step is I plug in the wave function:

##-\frac{\hbar}{2m}\frac{\partial^2Asin(kx-ωt)}{{\partial}x^2}+V(x,t)Asin(kx-ωt)=i\hbar\frac{{\partial}Asin(kx-ωt)}{{\partial}t}##

From here, I have a differential equation, which, I'm pretty sure I can't solve, but I'm mostly going off the fact that the question says to show that this wave function "does not satisfy.."

But I'm really unsure on how to show this..I don't remember a lot from DiffEq, but I can see that I can't do separation of variables here.
 
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Quote "I don't remember a lot from DiffEq". Time to do a good review, isn't it? To keep it simple assume V = 0 and do the partial derivatives. What do you get?
 
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I couldn't agree more.

##\frac{\hbar^2}{2m}Ak^2sin(kx-{\omega}t){\partial}x+0=-i{\hbar}A{\omega}cos(kx-{\omega}t){\partial}t##
 
Why have you written \partial x and \partial t at the end of the partial derivatives? That doesn't make sense. Just derive two times wrt. to x on the one side and once by t on the other and check that the given function doesn't fulfill the equation after you've sorted out all the constants.
 
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Got it, I've forgotten a lot. It's been over year since DiffEq, and a year before that since Cal 3. Thank you.

EDIT:

Actually, one last thing. Why can I let V=0?

EDIT: Nevermind, I think I see what is going on.

This may be overly simplistic, but basically in order for a wave function to satisfy the Time-Dependent Schrödinger equation, do we have to be able to reduce the equation down to:

##\hbar\omega=\frac{\hbar^2k^2}{2m}+V_o##
 
Last edited:

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