chemistry
posted by sam .
The electron from a hydrogen atom drops from an excited state into the ground state. When an electron drops into a lowerenergy orbital, energy is released in the form of electromagnetic radiation.
Part A: How much energy does the electron have initially in the n=4 excited state?
answer I got = 1.36*10^19 J
Part B: If the electron from Part A now drops to the ground state, how much energy is released?
the answer i got was 2.04*10^18 J
but i don't understand part :
What is the wavelength lambda of the photon that has been released in Part B?
can someone please explain this one to me, thank you

I didn't check your answers to A and B.
For the part you don't understand, subtract the energy of the electron in the two levels; that is the energy released. Then substitute into E = hc/wavelength and solve for wavelength.The unit for wavelength in this equation is meter. 
When an electron moves from the n=2 to n=4 state, Does it gain or lose energy? In a more to n=4, is a photon emitted or absorbed?