Hypothetical atom + Rydberg equation

[Quwes199]

Homework Statement

Consider the following energy levels of a hypothetical atom.
E4 -1.0 10-19 J

E3 -5.0 10-19 J

E2 -10 10-19 J

E1 -15 10-19 J
(a) What is the wavelength of the photon needed to excite an electron from E1 to E4?
_______nm
(b) What is the energy (in joules) a photon must have in order to excite an electron from E2 to E3?
_______J
(c) When an electron drops from the E3 level to the E1 level, the atom is said to undergo emission. Calculate the wavelength of the photon emitted in this process.
_______nm

Homework Equations

1/lambda= R(1/n^2-1/n^2)

The Attempt at a Solution

I have no idea where to start other than that equation... I did the ones that involved hydrogen but I'm stuck on these on... can you point me in the right direction?

 

[Borek]

This is an almost good equation. Problem is, as written it holds only for a hydrogen atom, while this is an "hydrogen-like" ion. There is a slightly modified version of the formula that includes Z (atomic number) and holds in this case.