# First-order correction

Demon117
1. Calculate the first-order correction to $$E^{3}_{(0)}$$ for a particle in a one-dimensional box with walls at x = 0 and x = a due to the following perturbations:

(a) H' = $$10^{-3}$$$$E_{1}$$x/a
(b) H' = $$10^{-3}$$$$E_{1}$$sin(x/a)

## The Attempt at a Solution

The only attempt that I have made is to start with the equation $$E_{n}$$=$$E^{(0)}_{n}$$+$$H'_{nn}$$. But I have not really gotten anywhere with it. Does anyone have any ideas where to start with this question?

## The Attempt at a Solution

fatin

Staff Emeritus
The first-order correction to the energy of state $|n\rangle$ is H'nn, which is the matrix element $\langle n|H'|n \rangle$. You just need to calculate that for the given state and perturbations.
The first-order correction to the energy of state $|n\rangle$ is H'nn, which is the matrix element $\langle n|H'|n \rangle$. You just need to calculate that for the given state and perturbations.