Burnaby North Secondary
Floor Location : J 146 D
In my project, I was researching about the number of beta particles that penetrate aluminum sheets (independent variable) being inversely proportional to their number. I chose this question because I have always been fascinated by radiation, and to do an experiment involving it would be very exiting for me. After thinking about this, I believe that the number of beta particles withheld by the metal linearly depends on the number of aluminum sheets.
First, I had to find a radioactive element that could emit beta particles. I found out that NoSalt® is a salt substitute and contains potassium chloride (radioactive) instead of natrium chloride.
Next, I went online and ordered 2 DIY Geiger counters. In the span of the next few weeks, I was working on soldering them together. I found this very amusing, but at first it was quite challenging.
After I have come up with a good experimental design and took care of my variables and controls, I started experimenting.
I put my Geiger counter (with a Geiger tube) inside a pan so that the amount of background radiation that reach the tube would be minimal. I put my potassium chloride in a thin zip lock bag and placed it on a Styrofoam slice that was separating the Geiger tube from the bag. I did this because the bag was quite heavy, (311 grams) and the pressure might have made the Geiger tube break or dent.
I then ran a program for counting CPM’s (count per minutes/particles) that was on their website. I measured results on “without any aluminum sheets” (5 tests) and then was continually adding aluminum sheets to the stack. The stack wasn’t generally getting higher because aluminum sheets are so very thin.
In conclusion, my hypothesis had been proven wrong. The dependency of aluminum sheets to the amount of radiation is exponential. The way I knew this was if you make a graph on an Excel spreadsheet, and then put a trend-line on the graph, you could either put a linear trend-line, or an exponential trend-line. If you put a linear trend-line you will realize that it doesn’t fit the graph, and doesn’t pass through as many points as possible. An exponential trend-line on the other hand, goes through most of the points and it is visible even to the naked eye that the dependency is exponential.