# Formula- first order correction to the n-th wave func

1. Oct 11, 2015

### Imperatore

Could anybody explain me why indeed we can express the first-order correction to the n-th wave function $$\psi_{n}^{1}$$ by linear combination $$\sum_{m} c_{m}^{(n)}\psi_{m}^{o}$$

2. Oct 11, 2015

### Staff: Mentor

The $\psi_n$ (if defined properly - you didn't specify where they come from) are a base of your vector space of wave functions. You can express every physical wave function with such a linear combination.

3. Oct 11, 2015

### Imperatore

It's Schrodinger equation to first order $$\lambda^{1}$$ You can see it on page 224 in the Griffiths' Introduction to quantum mechnics

4. Oct 11, 2015

### Imperatore

5. Oct 11, 2015