# Homework Help: Quantum mechanics

1. Sep 20, 2004

### DennisG

An electron in the hydrogen atom makes a transition from an energy state of principle quantum number N(i) to the N=2 state. If the photon emitted has a wavelength of 434 nm, what is the value of N(i)?

....no idea

2. Sep 21, 2004

### cepheid

Staff Emeritus
Hmm...my guess is that you determine the photon energy using the relation

$$E = \frac{hc}{\lambda}$$

Then you look up how large an energy transition (in "steps" of N) down to N = 2 is required for a photon of that energy to be emitted.