Consider a quantum mechanical system described by the Hamiltonian operator \(\hat H\), with eigenfunctions \(\psi_n\) and corresponding eigenvalues \(E_n\) such that: \(H^{ψ_n}=E_nψ_n\)
where
An arbitrary wavefunction \(\psi\) is expanded in terms of these eigenfunctions as: \(Ψ=n∑c_nψ_n\)
where are complex coefficients.
The expectation value of the Hamiltonian \(\hat H\) for this wavefunction
Which of the following statements about the expectation value \(<\hat H>\) is correct?