What Happens to the Wave Function When the Size of a Quantum Well Doubles?

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SUMMARY

The discussion focuses on the behavior of a particle's wave function when the size of an infinite quantum well is doubled from L to 2L. The wave function is initially defined as ψ = √(2/L) sin(nπx/L), and the energy is given by E = n²π²h²/(2mL²). To determine the new wave function at a later time t, the initial state must be expressed as a superposition of states in the larger well, requiring recalculation of coefficients cn for the new boundary conditions. The presence of decay mechanisms can influence the energy transition between states.

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Homework Statement



there is a infinite quantum well with size L and there is a particle in it with mass m. suddenly the size of the quantum well is doubled. What will be the wave function at a later time t ?

Homework Equations



ψ= [itex]\sqrt{2/L}[/itex] sin (n pi x / L)

E = n^2 pi^2 h^2 / 2mL^2

The Attempt at a Solution



do we need to find cn again with 2L ?
 
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Yes.
I'd normally do this by expressing the initial state of the particle, in the 1L well, in terms of a superposition of states of the final 2L well... then finding the time-evolution of those states.

I'd have expected the initial state to be a specified n state (i.e. the ground state).

A lot depends on context - eg.
If there is a mechanism for decay present, then the question could be answered in terms of the energy lost in the decay from initial to final states. (Otherwise the system remains in a composite state until some measurement of energy is made.)
 

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