# Particle in a box, some clarification please

1. Dec 8, 2013

### rwooduk

the energy of an n state can be given by:

E = (nh)^2 / 8mL^2

is this a representation of the Kinetic energy of the particle? i thought it was but this question has got me confused.

it asks for the Energy of the n=1 state, which ive done. then it asks what quantum number, n would be needed if the Kinetic Energy was 0.025eV.

i rearranged the above eqn for n and put E= (0.025ev X 1.6x10^-19 ), but get something stupid as a result.

so, is E the energy of the state of the particle OR it's kinetic energy OR both?

Thanks in advance for any help.

2. Dec 8, 2013

### hjelmgart

Hmm, the energy state is the total energy, but as you only have kinetic energy, it should be straight forward, as you've done.

3. Dec 8, 2013

### ShayanJ

The potential in the case of particle in a box problem,is zero inside the box and greater than zero outside it.So inside the box,the total energy of the particle is equal to its kinetic energy.

4. Dec 8, 2013

### rwooduk

yes this is as i suspected, i get a stupidly high number for n and its not a whole number either! will recalculate.

thanks for the replies!!

5. Dec 8, 2013

### hjelmgart

Well, getting a whole number for n is quite unrealistic, when you think about the numbers and decimals, you are using.

Also I don't think there are any limits for the quantum number for a particle in a box.