A xx.x eV electron collides with a hydrogen atom at rest in its ground state, exciting the atom to various states.

a)What is the largest value of n that can be reached considering conservation of energy?

n =

b) After having been excited to the highest possible n, which of the following photon energies cannot be emitted by subsequent decays?

1.9 eV
4.2 eV
10.2 eV
12.1 eV

Answer = eV