Angular momentum of hydrogen atom in specific energy level

[accountkiller]

Homework Statement

A hydrogen atom is in a state with energy -0.278 eV.

Homework Equations

L = nh'

The Attempt at a Solution

The answer book says to do E_n = (-13.6 eV)/n^2 but I can't find this equation in our book. Is the 13.6 a significant number or just a different number they used for a different problem?

I know I can do this all by myself when I have time to study, but I just want to get this homework done quickly tonight to get it out of the way, since I also have a math quiz tomorrow. I promise I'm usually a good student. I'd appreciate any quick help, thanks!

 

[Thaakisfox]

The 13.6eV is the Rydberg constant.