The energy of the photon created by coherent scattering is equal to which of the following?

• A. sum of the original photon energy and the electron binding energy
• B. energy of the original photon
• C. inner shell electron binding energy
• D. difference between the original photon energy and the electron binding energy

Answer: (B)

In coherent scattering, also known as Rayleigh scattering, the photon interacts elastically with the entire atom. There is no transfer of energy to the electrons, so after the interaction the atom returns to its original state and the scattered photon keeps the same energy as the incoming photon. The only change is in direction, not in energy. That’s why the energy of the photon produced is the same as the original photon energy.

This wouldn’t involve any electron binding energy changes or energy loss, which is why options that add energies, involve inner-shell binding, or subtract energy aren’t correct. In contrast, energy loss occurs in inelastic processes like Compton scattering, where the scattered photon has less energy than the incident one.