# Kinetic energy of electron & energy states

1. Mar 11, 2013

### Kognito

1. The problem statement, all variables and given/known data

Use the relationship kinetic energy E = p^2/2m to show that the energy $E_{0}$ of an electron of mass m in its lowest energy state is given by $E_{0}$ = h^2/8mL^2

2. Relevant equations

E = p^2/2m

$E_{0}$ = h^2/8mL^2

3. The attempt at a solution

I've stared at this for far too long, googled it to death as well as checked through all my course materials and I can't seem to get started with it. Any ideas at all would be welcome.

Kognito

2. Mar 11, 2013

### Pagan Harpoon

What is L here? Is the electron in a 3d box and L is the side length? Does the problem say what boundary conditions it wants you to apply at the box edges?

3. Mar 11, 2013

### Kognito

My apologies, I missed that off the end of the sentence (too busy messing with equation formatting controls).

But yes, L represents a box within which the electron resides. The question doesn't specifically mention boundary conditions though the previous part of the question said to draw the electron in its lowest energy state, able to move freely along the length of the box, as represented by a standing wave.

4. Mar 11, 2013

### Pagan Harpoon

There's two things you can do... one is write down the Schrodinger equation and then solve it.

The other is to say that the electron's wavefunction has to have nodes at the box edges, so write down an expression for its deBroglie wavelength and apply the appropriate constraints to it.