Quantum Physics For Dummies, Revised Edition
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In quantum physics, in order to find the energy of a perturbed system, En, you need to start by calculating the energy and wave function of an unperturbed system. You start with the energy:

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Then add the first-order correction to the energy,

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and add the second-order correction to the energy,

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Now what about the wave function of the perturbed system,

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Start with the wave function of the unperturbed system,

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Add to it the first-order correction,

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And then add to that the second-order correction to the wave function,

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Note that when

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becomes the unperturbed energy:

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and

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becomes the unperturbed wave function:

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So your task is to calculate E(1)n and E(2)n, as well as

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So how do you do that in general? Time to start slinging some math. You start with three perturbed equations:

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You then combine these three equations to get this jumbo equation:

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About This Article

This article is from the book:

About the book author:

Steven Holzner is an award-winning author of technical and science books (like Physics For Dummies and Differential Equations For Dummies). He graduated from MIT and did his PhD in physics at Cornell University, where he was on the teaching faculty for 10 years. He’s also been on the faculty of MIT. Steve also teaches corporate groups around the country.

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