Which of the following transition leads to the emission of high energy photons?

A B C D

D

During emission, the electron make a transition from higher excited state to lower excited state. The energy of nth excited state is given by  En = -13.6/n2 So, E2-E1 = 10.2 eV E3-E1 = 12.09 eV This clearly shows that the transition D will release high energy photon.