# Homework Help: Energy of a photon

1. May 16, 2004

### UrbanXrisis

What is the energy of a photon when the Hydrogen atom transitions from the n=4 to n=3 energy state?

2. May 16, 2004

Find the difference in potential between the n=3 and n=4 states.

3. May 16, 2004

### UrbanXrisis

what formula do I use to find the energy in each state?

4. May 17, 2004

### Janitor

If you aren't worried about small relativistic corrections, just take the difference of R/n^2 for n=3 and n=4, where R is the Rydberg constant. Here n is the principle quantum number.

5. May 17, 2004

6. May 17, 2004

### UrbanXrisis

would energy be in Joules?

7. May 17, 2004

### UrbanXrisis

so to find the difference in potential... E=(R/3^2)-(R/4^2) ?
E=533264 J?

8. May 17, 2004

That's a little much... Look about 2/3 down the webpage I linked to.

eV is more commonly used, but Joules works.

9. May 17, 2004

### UrbanXrisis

is 533264 Joules a lot for the difference in the energy states?

10. May 17, 2004

### Janitor

The Rydberg constant is about 13.6 electron volts. So if you want energy in those units, it would be 13.6*(1/9 - 1/16).

The onversion from electron volt to joule is accomplished by multiplying by 1.602 x 10-19. So your number of joules is way too high.