Problem 12.1

Position Graph  Velocity Graph n =   Position Graph Momentum Graph

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The normalized classical probability distributions and quantum-mechanical probability densities for the harmonic oscillator are shown in position and momentum space.

  1. Click on Position Graph below the right-hand graph.  The graph shows the probability that a particle is in the ground state at some position x.  You may vary n to see higher energy states.  Under the left-hand graph, a ball is attached to a spring and the spring is initially stretched.  What does the classical probability distribution of finding the particle as a function of x look like?   Briefly discuss your reasoning.  After you answer, click  Position Graph below the left-hand graph and check yourself.   Did your answer agree with the given answer.  Explain why or why not.

  2. Under what conditions would the right-hand graph look like the left-hand graph?  In other words, what is the correspondence between the classical and quantum position probabilities of a particle in a harmonic oscillator potential energy function?  Check your answer using the above "Position Graph" buttons.

  3. Click on Momentum Graph on the right-hand graph.  Displayed is a graph of the probability density in momentum space as a function of p.  The box <p> gives the expectation value of the momentum of the particle.  Now click on Velocity Graph on the left-hand graph.  What is the difference you see?  Why does this difference exist? 

 

 

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