# Difference in atomic energies 2p 1s for hygrogen and duterium

1. Dec 31, 2011

### helpcometk

1. The problem statement, all variables and given/known data
Calculate the difference in
wavelength between the 2p→1s line in ordinary hydrogen and in deuterium (which has a nucleus containing
a proton and a neutron).

2. Relevant equations

the difference in wavelength is related with the difference in frequences with the relationship :
c=(Δλ) (Δf) but Δf =hbar/ΔE so Δλ= c ΔΕ / hbar ,so what's the difference in energies between 2p and 1s ?
3. The attempt at a solution

2. Dec 31, 2011

### vela

Staff Emeritus
c = (Δλ) (Δf) can't be right. If Δf = 0, you'd have Δλ = 0, and c clearly doesn't equal 0.

Think about why the energies would be different in the two atoms. What's the primary difference between ordinary hydrogen and deuterium? Why would this affect the energy levels? Think about the assumptions that went into deriving the formula for the energy of a state.

3. Dec 31, 2011

### helpcometk

That was the first part of the formal question actually and ive hidden it becuase in knew the answer, there is reduced mass differnce between deuterium and Hydrogen.
But what cant understand is the difference between 2p and 1s in an individual atom

4. Dec 31, 2011

### vela

Staff Emeritus
Hmm, I have to admit I'm confused at to what exactly you're getting stuck on. Can you be more specific?

5. Dec 31, 2011

### helpcometk

Is 2p state correspondin to n=2 and 1s to n=1 ?

6. Dec 31, 2011

### vela

Staff Emeritus
Yes.

7. Dec 31, 2011

Thanks