# Homework Help: Eigenfunction problem

1. Oct 4, 2009

### noblegas

1. The problem statement, all variables and given/known data
Consider a particle that moves in one dimension. Two of its normalized energy eigenfunctions are $$\varphi_1(x)$$ and $$\varphi_2(x)$$, with energy eigenvalues $$E_1$$ and $$E_2$$.

At time t=0 the wave function for the particle is

$$\phi$$= $$c_1*\varphi_1+c_2*\varphi_2$$ and $$c_1$$ and $$c_2$$

a) The wave functions $$\phi(x,t)$$ , as a function of time , in terms of the given constants and initials condition.

b) Find and reduce to the simplest possible form, an expression for the expectation value of the particle position, $$<x>=(\phi,x\phi)$$ , as a function , for the state $$\phi(x,t)$$ from part b.

2. Relevant equations

3. The attempt at a solution

for part a, should i take the derivative of $$\phi$$ with respect to t?

2. Oct 4, 2009

### Matterwave

For part a you need to use the Schroedinger's equation to know how the state evolves as a function of time, but you need to know the potential the particle is in...does the problem specify a potential?

3. Oct 5, 2009

### noblegas

No , they don't specify the value of the potential