A hydrogen atom in an n = 2, l = 1, m1 = -1 state emits a photon when it decays to an n = 1, l = 0, m1 = 0 ground state.
(a) In the absence of an external magnetic field, what is the wavelength of this photon?
(b) If the atom is in a magnetic field in the +z-direction and with a magnitude of 2.20T, what is the shift in the wavelength of the photon from the zero-field value? Does the magnetic field increase or decrease the wavelength? Disregard the effect of electron spin.