## College Physics (4th Edition)

We can find the new energy of the hydrogen atom: $E_f = E_0+12.1~eV$ $E_f = (-13.6~eV)+12.1~eV$ $E_f = -1.5~eV$ We can find the new energy level: $E_f = \frac{E_0}{n^2}$ $n^2 = \frac{E_0}{E_f}$ $n = \sqrt{\frac{E_0}{E_f}}$ $n = \sqrt{\frac{-13.6~eV}{-1.5~eV}}$ $n = 3.0$ The hydrogen atom is excited to the third energy level.