Yet more

RE: the last quiz, second problem.

You have only 3 possible energy levels. Photons can only be emitted when you have an electron changing from a higher level to a lower one. Here we have

E1 = 1.2eV
E2 = 2.4eV
E3 = 4.8eV

The only photons that can be emitted must correspond to differences between energy levels:

E3-E2 = 2.4eV
E2-E1 = 1.2eV
E3-E1 = 3.6eV

So three types of photons can be emitted: when an electron jumps from level 3 to 2, from 2 to 1, or from 3 to 1. Given these energies, convert to joules:

E=(2.4eV)(1.6e-19 J/eV) = 3.84e-19 J

Once you have that, use E = hc/(wavelength) and solve for wavelength. You should get about 1e-6, 5.17e-7, and 3.44e-7 meters.