OSU Radiation Center Half-life Experiment


You have been provided with a bag of M&M or Skittles for this experiment.  Shake the bag then cut a strip off one end of the bag so the entire end is open.  Carefully pour (a gentle throw of the dice) the “unstable atoms” out on a paper plate or clean flat surface.  Remove the blank “decayed” atoms (no label showing) counting the atoms as they are removed.  Record the number of atoms removed.  Place the remaining atoms back in the bag.  Hold the open end closed and shake.  Your sample of atoms has progressed through one half-life.  Don’t forget to properly dispose of the decayed atoms that you removed “if you know what I mean Vern.”


Repeat this process pouring the atoms and counting the blanks until all of the atoms are gone recording the number of atoms removed (decayed) for each throw.  By definition the half life is the time required for a decaying population to decrease 50%.  This is very similar to flipping coins.  Use approximately 100 pennies if you want to repeat the experiment.


 Advanced Exercise:  If you have access to a computer, try entering your decay series into a column in an Excel spreadsheet.  Create an X Y scatter chart from the data series.  Add a trend line with logarithmic function and display the equation on the chart.  The exponent in the equation is the negative Decay Rate constant which is also equivalent to the Slope of the line.  Half-life is the natural log of 2 divided by the Rate Constant (ln(2)/k).


Are you able to complete the Advanced Exercise?  Talk with you instructor about arranging an Aluminum Half-Life lab with Oregon State University Radiation Center (541-737-2341).  We are able to accommodate groups of 10 to 24 students.


Sponsored by: Oregon State University Radiation Center, Departments of Radiation Health Physics and Nuclear Engineering, Corvallis, Oregon 97321, 541-737-2341, Fax: 541-737-0480, http://radiationcenter.oregonstate.edu/