How Can Quantum Mechanics Constants Be Deduced from Average Energy?

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SUMMARY

The discussion focuses on deducing constants from a normalized wave function in quantum mechanics, specifically using the average energy formula pi^2hbar^2/(ma^2). The wave function is expressed as PSI = c_1 psi_1(x) + c_2 psi_1(x), where c_1 and c_2 are coefficients corresponding to the ground and first excited states. Participants confirm that the wave function represents a linear combination of states, emphasizing the importance of orthonormal basis functions and the normalization condition that the sum of the squares of the coefficients equals one. The total energy is derived from the product of coefficients and eigenenergies.

PREREQUISITES
  • Understanding of quantum mechanics principles, particularly wave functions
  • Familiarity with eigenstates and eigenenergies in quantum systems
  • Knowledge of normalization conditions for quantum states
  • Basic grasp of potential wells, specifically one-dimensional infinite potential wells
NEXT STEPS
  • Study the concept of energy expectation values in quantum mechanics
  • Explore the derivation of eigenenergies for a one-dimensional infinite potential well
  • Learn about orthonormal basis functions and their applications in quantum mechanics
  • Investigate linear combinations of quantum states and their implications for quantum systems
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Students and professionals in physics, particularly those specializing in quantum mechanics, as well as researchers exploring wave functions and energy states in quantum systems.

greisen
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Hey,

I have a normalized wave function

PSI = c_1 psi_1(x) + c_2 psi_1(x)

where c_1 and c_2 are constants with the eigenfunctions equal to ground and first excited state. The average energy of the system is pi^2hbar^2/(ma^2) - what can one deduce about the constant and how?

Thanks in advance
 
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greisen said:
Hey,

I have a normalized wave function

PSI = c_1 psi_1(x) + c_2 psi_1(x)

where c_1 and c_2 are constants with the eigenfunctions equal to ground and first excited state. The average energy of the system is pi^2hbar^2/(ma^2) - what can one deduce about the constant and how?

Thanks in advance

I'm thinking energy expectation value, similar to your problem on creation/anihiliation. What are the eigenenergies of the two states?
 
The particle is in a one dimensional well with V(x) = 0 for o <= x <= a and otherwise it is infinity. Is it a linear combination between the two states ?

Again thanks very much
 
greisen said:
The particle is in a one dimensional well with V(x) = 0 for o <= x <= a and otherwise it is infinity. Is it a linear combination between the two states ?

Again thanks very much
Yes it is a linear combination of states. With orthonormal basis functions and normalized PSI the sum of the squares of the coefficients has to be 1. The products of coefficients times eigenenergies has to be the total energy
 

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