- #1
rwooduk
- 762
- 59
Homework Statement
Consider a one-dimensional particle subject to the Hamiltonian H with wavefunction [tex]\Psi(r,t) =\sum_{n=1}^{2} a_{n}\Psi _{n}(x)e^{\frac{-iE_{n}t}{\hbar}}[/tex]
where [tex]H\Psi _{n}(x)=E_{n}\Psi _{n}(x)[/tex] and where [tex]a_{1} = a_{2} = \frac{1}{\sqrt{2}}[/tex]. Calculate the expectation value of the Hamiltonian with respect to [tex]\Psi (x,t)[/tex]? Which energy eigenvalue is the most likely outcome when we measure the energy of particle once?
Homework Equations
Given in the question.
The Attempt at a Solution
[tex]\Psi(r,t) =\sum_{n=1}^{2} a_{n}\Psi _{n}(x)e^{\frac{-iE_{n}t}{\hbar}}[/tex]
let [tex]\Psi_{1}(r,t) =a_{1}\Psi _{1}(x)e^{\frac{-iE_{1}t}{\hbar}}[/tex] and [tex]\Psi_{2}(r,t) =a_{2}\Psi _{2}(x)e^{\frac{-iE_{2}t}{\hbar}}[/tex]
therefore [tex]\left \langle H \right \rangle = \left \langle \Psi _{1}+ \Psi _{2}|H |\Psi _{1}+ \Psi _{2}\right \rangle[/tex]
which gives [tex]\left \langle H \right \rangle = (E_{1}+ E_{2}) \left \langle \Psi _{1}+ \Psi _{2}|\Psi _{1}+ \Psi _{2}\right \rangle[/tex]
but not sure what to do now? is this the best way to do this? the trouble I am having is using bra ket notation to work with a sum of wavefunctions.
any advice on this would really be appreciated!
thanks in advance