Make sure your active source is Gamma rays (Ba-137). Set the material to Lead. Record the counts for 15 seconds. Thickness Counts in 10 seconds Counts Thickness Counts (mm) Trial 1 Trial 2 Trial 3 Average (mm) Average 1.1 150 134 114 132.6667 1.1 132.6667 3.4 95 103 104 100.6667 3.4 100.6667 5.8 94 85 72 83.66667 5.8 83.66667 7.7 80 70 72 74 7.7 74 13 69 51 50 56.66667 13 56.66667 15.4 46 40 51 45.66667 15.4 45.66667 22.4 37 25 15 27 22.4 27 27.4 17 22 20 19.66667 27.4 19.66667 Place Graph down here Which type of curve fit the data best? Roughly what thickness of lead was needed to cut the number of counts in half