1. (5 pts) A radioactive source emitting ALPHA DETECTORS (2) IDENTIFY LUNAR SURFACE ATOMS BY MEASURING ENERGY OF ALPHA PARTICLES RADIOACTIVE REFLECTED FROM NUCLEI OF ATOMS SOURCES (6) 6.1 MeV *He particles was flown on OF ALPHA PARTICLES the final three Surveyor lunar lander missions to determine the composition of the lunar surface by PROTON DETECTORS 141 DENTIFY LUNAR SURFACE ATOMS BY MEASURING ENERGY NUCLEI OF ATOM'S BY Rutherford scattering. A diagram of ALPHA PARTICLES the setup is shown to the right . The detector for detecting scattered He was placed at 175. a. (1.5 pt) Calculate the energy FIG. 2. Cut-away Diagram of the Sensor Head of the Alpha Scattering Lunar (in the lab frame) of the alpha Chemical Analysis Instrument. The box and bottom plate have a 10 cm diameter opening through which the alpha particles strike the sample underneath. Indicated particles scattered into the are the geometrical relationships of the sources to the alpha and proton-detectors. The proton detectors are covered with thin gold foils that stop alpha particles, but allow detector at 175 assuming an most of the protons to get through [ze]. infinitely thin lunar sample containing Fe and O. b. (1.5 pt) Assuming the composition is FeO2, make a graph of the energy (on the x-axis) vs the relative intensity (y-axis) of alpha particles scattering from the Fe and the O. c. (1 pt) If the detector were placed at 25 (which we can't do on the moon!), what are the energies of the alpha particles scattered from Fe and O? All else being equal, would you prefer an angle of 25 or 175 to perform material analysis using Rutherford scattering? Why? d. (1 pt) In reality, the sample is not infinitely thin, but instead is thicker than the range of the alpha particles (i.e. the alpha particles lose energy as they traverse through the material, ultimately stopping in the material). How will your graph in part (b) change? Sketch the graph you expect in this case, briefly explaining the reasoning behind your