A) A hydrogen atom is excited in the n = 4 state. Unexpectedly the atom losses energy by emitting a photon. Subsequent to the emission the hydrogen atom turns out to be in the n = 2 state. Explain what is the wavelength of the emitted photon?
B) The atom is still in the n = 2 state. Is a photon of wavelength 375 nm enough to ionize this hydrogen atom?