Nuclear fission: If a 2.0-MeV neutron released in a fission reaction loses half of its energy in each moderator collision, how many collisions are needed to reduce its energy to (1/25) eV?

Question

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The energy of the neutron is halved with each collision. Starting from 2.0 MeV, we need to find how many halvings are required to reach (1/25) eV. Convert 2.0 MeV to eV: 2.0 MeV = 2,000,000 eV. The energy after n collisions is (2,000,000 eV) * (1/2)^n. Set this equal to (1/25) eV and solve for n: (1/2)^n = (1/25) / 2,000,000. Solving gives n ≈ 26.

Nuclear Fission: If a 2