Question 1 The sun generates its energy through nuclear fusion, making helium from hydrogen. The main process by which this happens, called the proton-proton chain, goes as follows: - Two protons come together to create deuterium, a positron, a neutrino, and energy: p + p _. D + e'r + v + energy - The deuterium fuses with another proton to make 3He: D + p > 3He + energy - Fianlly, 4He is produced by fusing two 3He nuclei together: 3He + 3He _. 4He + p + p + energy What is the total energy released during the creation of one 4He nucleus? Give your answer in MeV, and remember that you need to make two 3He nuclei in the process. Be sure to use at least ve signicant gures for your masses, but your nal answer should have three or four sig gs. 2832 MeV Question 2 Nuclear medicine often uses radioactive samples as a tracer to monitor processes inside the body. Suppose a nuclear reactor makes a certain isotope sample with an initial activity of 179 mCi, and the sample gets delviered to a hospital 18.0 hours later, when its activity has become 78.4 mCi. Luckily, the sample remains usable until its activity drops below 13.6 mCi. How long after the delivery is this sample usable? l