Chemistry 11 Lab #21

Radioactivity

Safety:  Radioactive materials and lead are very dangerous if consumed.  The sealed samples of radioactive materials are safe as long as they remain sealed.  I will set the samples up in suitable locations so that you need not even touch them.  Simply move the Geiger counter detector to the sample. Avoid handling the lead shielding and wash your hands after handling it.

 
Modeling decay and half-life

1. Get 64 “coins” and find a clear area of lab bench.  Choose a side of the coin you will call heads.
2. Gather the coins in your hands and shake them up.  Toss them on the bench and remove all the heads.  Count the coins remaining and enter the result in the table below under the column labeled “Experimental.”
3. Repeat step 2 with the remaining coins until no coins remain.
4. Calculate a theoretical value for each step and fill in the table column labeled “Theoretical.”
5. Graph the results from both the “Experimental” and “Theoretical” columns on a single graph.

 

 

Effect of shielding on gamma radiation

1. Go to the Geiger counter station.  I will give you a brief tour of the equipment and how to use it.
2. Take a reading to find the background radiation level by keeping the detector far from the sources and reading the counts per minute from the dial.
3. Position the detector near the radioactive source and take a reading.  Subtract the background reading and note the result.
4. Repeat step 3 with a shield of paper, then aluminum foil and then a piece of lead.  Compare the 4 results.

Effect of distance on radiation levels

1. Start with step 3 in the previous section.  Then increase the distance between the detector and source 1 cm at a time and take another reading and subtract background. 
2. Tabulate the results with columns headed Distance (in cm), 1/(distance squared) and Counts/min.
3. Graph 1/(distance squared) on the x axis and Counts/min on the y axis.  Note the shape.