# Wavelength of a photon homework

1. Jun 25, 2007

### Fiza43

what is the wavelength of a photon emitted when a hydrogen electron drops from the n = 6 to the n = 3 level?
(E1 = -13.6 eV and Planck's constant is 6.626 * 10^-34 J s)

2. Jun 25, 2007

### Staff: Mentor

Look up the Bohr model for hydrogen.

3. Jun 25, 2007

### CompuChip

Or take a quantum mechanics book which will tell you that
$$E_n = - \frac{m}{2 \hbar^2} \left( \frac{e^2}{4 \pi \epsilon_0} \right)^2$$
are the energy levels of a hydrogen atom (I checked this in Mathematica, filling in the numbers and n = 1 indeed gives -13.6057 ElectronVolt :D).

 In fact, $$E_n = \frac{E_1}{n^2}$$ (Griffiths, Introduction to Quantum Mechanics, p. 149, [4.70]). Now if that doesn't make it easy on you, I give up :) [/edit]

Last edited: Jun 25, 2007