Part 1: Qualitative Shielding Observations 1. Open up the Excel sheet for this lab. This is where you will record the data and answers to questions. 2. Go to http://thephysicsaviary.com/Physics/Programs/Labs/RadioactiveShieldingLab/ 3. Click Begin. You will see a radioactive source decaying, a counter, a time display, shield material, and shield thickness. It should look like this: Radioactive Shielding Lab Barium 137 y Decay Time Activity 5.3 s 232 0 decaysis Source to Defector Distance: 108 mmm Shield Information Aluminum Shield Thickness 15.2 mm 4. By clicking the displays you can change them. Clicking the "Barium" box will change to Radium, then to Carbon 14, then back to Barium. The decay is given by the Greek letter: v is Gamma (Barium), B is Beta-minus decay, a is Alpha decay. Keep the Shield Thickness where it was at the beginning (generally between 15 mm and 18 mm). For each type, record in the table in Excel which isotope it is (for Gamma decay, it is Barium-137, which is already filled in), then try each shielding material (click shield information material, such as Aluminum, to change) and wait until the timer reaches 15 seconds, then press Hold; record the number of counts. Switch to the next material, wait 15 seconds, record the counts. Generally, you will need to click Reset to start the counting and timer; click Hold when you get to 15 seconds. It's tough to stop it exactly on 15 seconds; if you're close that's good enough. After acquiring your data answer the questions in the Excel sheet. Part 2: Blocking Gamma Rays with Lead, Analysis and Graph 1. Reset and make sure your active source is of Gamma Radiation. 2. Set the shield material to Lead. You will vary the thickness to ten different thicknesses. For each thickness, record the number of counts received in fifteen seconds. Do each thickness three times. You will then average the counts. 3. Copy the Thickness column over to the right in the Excel sheet and copy the Counts Average column also. Create a graph of Average Counts vs. Thickness in mm. Do a curve fit for the graph (it's NOT a line). Try the different curves, make sure to display the R value, and see which graph type gives you the highest R value. Record that in the Excel sheet. 4. By looking at your graph and data, estimate what thickness of lead was needed to cut the number of counts in half (compared to the thinnest lead). Use the curve fit graph to determine this. 5. Save your Excel file and upload to DZL, Assessments, Assignments, Lab 13