Make a graph of the number of surviving particles

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Make a graph of the number of surviving particles versus the number of sheets of material. Since each sheet is a specific thickness of material, you now have a graph of how the surviving amount of radiation depends on the thickness of material. Try to guess what functions could 197
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SHIELD THICKNESS – 1202Lab8Prob3 represent this graph. Check your guesses by graphing them to see if they match your points. 4. Imagine that all of the sheets of material are very thin and are pushed together to make one thick piece of material. As the particles pass through a thin sheet, the number entering the next sheet is reduced. On what quantity(ies) does this change in the number of particles depend? Write an equation for the change of the number of radiation particles per small amount of thickness (dN/dT). Solve this equation for the surviving number of particles as a function of material thickness. Check to see if this function matches your graph in question 3. 5. Compare the mathematics for your hypothetical description of the shielding of radioactive particles by material to that of radioactive decay described in your textbook. How are they similar? Different? P REDICTION Write down a mathematical function that describes the effect of material thickness on the intensity of radiation that passes through that material. Describe the reasoning that leads you to that function. E XPLORATION WARNING: The radioactive sources available for this problem provide low intensity radiation, and are safe if handled with respect for short amounts of time. Do not remove them from the laboratory, and do not attempt to open the plastic disks containing the sources. If a disk breaks open inform your TA immediately, do not touch it. Make sure you read the Equipment and Software appendices to understand the operation of the Geiger counter before trying to operate it. Place a radioactive source near the detector, turn on the counter. Try the controls, and make sure every group member understands how to operate it. Try each of your sources to make sure the equipment is functioning . With the detector working you now need to determine how to make your measurement uncertainty as small a practical. Start by using the detector to measure the number of counts from a radioactive source in some short time interval, say 10 or 15 seconds. Repeat this measurement several times, recording the number of counts occurring in each fixed time interval. Compute the average number of counts per second and the difference of each trial from that average. Calculate the average of these differences for all of your trials. That average difference represents your counting uncertainty for the measurement. Now increase your time interval by a factor of 4 and repeat the same 198
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