An electron in a hydrogen atom is in an excited state of 3d transitions radiatively to the 2p energy level, without regarding the spin-orbit interaction:
a. Show the energy level splitting of 3d and 2p if there's no magnetic field and with magnetic field B in one energy level diagram.
b. What are the allowed transition conditions and show it on the energy level diagram above.
c. Emitted energy if external magnetic field B = 0.
d. Emitted energy if it's in a room with magnetic field B = 1 T.