Quantum Mechanics wavefuction collapse

1. The problem statement, all variables and given/known data
Consider a harmonic oscillator. It is in the ground state. Momentum is
measured and is found to be between 0.2 $$\sqrt{}m\omega h$$and 1.5 $$\sqrt{}m\omega h$$. (h here is h bar)
Energy is now immediately measured. What is the probability that the energy is
unchanged? You may want to do it numerically.

2. Relevant equations

3. The attempt at a solution
I dont know what to start with. Maybe P(E unchange)=|<$$\varphi$$0|wave after measurement>|2

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 Recognitions: Gold Member Homework Help Science Advisor Staff Emeritus That's right. If the energy is unchanged, it's in the ground state, so you want to find the probability the oscillator is in the ground state after the momentum is measured.
 how to find wave after measurement then?

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