E =hc Here the hc is equal to the 1240 eV x nm. How did they this when h = 6.626 x 10³⁴, and c = 3.0 x 10⁸. When I multiply these two together, I get 1.9878 x10^-25. Do I somehow need to change this to electron volts? If so, how do I change hc to this?

Solution E = he 1240 e V.nm = 0.969 e V 1280 nm Looking at the energy level diagram, the photon must be in the Paschen series. Therefore, the final state is n = 3 and the final energy is E3 = -1.51 eV. energy of photon = E; - Ef