question_answer 28)

  Let be the energy of the nth  level of H-atom. If all the H-atoms are in the ground state and radiation of frequency /h falls on it, (a) it will not be absorbed at all (b) some of atoms will move to the first excited state (c) all atoms will be excited to the n = 2 state (d) no atoms will make a transition to the n = 3 state

Answer:

  is the energy of nth level of hydrogen atom. If all the H-atom are in ground state, (n = 1), then the radiation of frequency (E-2 ? E1)/h falling on it may be absorbed by some of the atoms and move them to the first excited state (n = 2). All atoms may not be excited to n = 2 state. Further, as (E2 ? E1)/h is sufficient only to take the atom from n = 1 state to n = 2 state, no atoms shall make a tansition to n = 3 state. Choices (b) and (a) are correct