An atom is excited to an energy state that is 5.9 eV above the ground state and then…
PHYSICS · Single correct · A Level · Physics · Particles and radiation · Particles and radiation
Problem
An atom is excited to an energy state that is 5.9 eV above the ground state and then returns to the ground state by emitting two photons in a cascade. Which of the following statements best describes the relationship between the energies of the two emitted photons and the original excitation energy?
(a) No definite statement can be made about the sum of the photon energies because the energy of the intermediate state is unknown.
(b) Each photon must have exactly 2.95eV, sharing the 5.9eV excitation energy equally.
(c) The sum of the photon energies must be exactly 5.9eV because energy is conserved across the two-step transition.
(d) The total photon energy is slightly less than 5.9eV because some of the excitation energy becomes kinetic energy of the recoiling atom.