Light emitted during the de excitation of electron from n = 3 to n = 2, when incident on a metal, photoelectrons are just emitted from that metal. In which of the following de excitations photoelectric effect is not possible? [Karnataka CET 2013]

The photoelectric effect is possible when light of sufficient energy incident on metal surface. When electron de-excites from n = 3 to n = 2, the light produces photoelectric effect. So, for the given options, the photoelectric effect is not possible for that level in which energy of emitted light is less than that for n = 3 to n = 2. Since,  $(hv{)}_{4\to 3}<(hv{)}_{3\to 2}$

Hence, photoelectric effect is not possible from n = 4 to n = 3.