In elastic scattering of neutrons, what happens to the kinetic energy?

• A. It is converted to heat in the nucleus
• B. It is not transferred to the nucleus
• C. It is transferred to the nucleus without excitation
• D. It is absorbed by the electron cloud

Answer: (C)

In elastic scattering, kinetic energy is conserved and shared between the two bodies without exciting internal states. When a neutron hits a nucleus, they exchange some momentum, and the neutron slows while the nucleus recoils. The energy that leaves the neutron appears as the recoil kinetic energy of the nucleus, with no energy put into exciting nuclear levels. The total kinetic energy before equals the total kinetic energy after, just redistributed between the neutron and the nucleus.

That’s why the best description is that the energy is transferred to the nucleus without excitation—the nucleus gains recoil energy rather than internal or electronic excitation. The other ideas would require either energy to go into internal nuclear states, remain entirely with the neutron, or be absorbed by the electrons, which doesn’t happen in elastic scattering.