Cracking the SAT Physics Subject Test
- How much energy must a ground-state electron in a hydrogen
atom absorb to be excited to the n = 4 energy level?
- When the electron is in the n = 4 level, what energies are
possible for the photon emitted when the electron drops to a lower
energy level?
Here’s How to Crack It
- For an electron to make the transition from E 1 to E 4 , it must absorb
energy in the amount E 4 − E 1 = (−0.85 eV) − (−13.6 eV) = 12.8 eV.
- An electron in the n = 4 energy level can make several different
transitions: It can drop to n = 3, n = 2, or all the way down to the ground state,
n = 1.
So, there are three possible values for the energy of the emitted
photon, E4 → 3, E4 → 2, or E4 → 1:
