Practice at reflecting on your
experimental results.
Practice at scaling graph
axes to uncover functions (models) that fit your data
Radiation background
Before you sign a radiation source out, you need to measure the
background radiation in the room, measured by your Geiger counter.
Start your counter and a timer to measure the background counted in
20 minutes. Once started, you can work on the LEARNING CATALYTICS QUESTIONS 1-3.
When your 20 minute count is done, answer LEARNING CATALYTICS QUESTIONS 4-7.
First Attenuation Measurements
Once you have a source in place, check that the distance is
set to 0.8 cm (keep this the same through all measurements).
Measure the radiation counts in 2 minutes.
Next measure the radiation counts with 3 sheets of aluminum
placed over the source (the thickness labelled 'C')
Is the thickness of three of these sheets of aluminum
sufficient to make your measured count-rate consistent with the
background count-rate? (you will need to divide by the number of
minutes to get a rate in counts/minute) LEARNING CATALYTICS QUESTIONS 8-10.
Measuring Radiation Attenuation
Now that you have established the amount of aluminum needed to
reduce the count-rate close to background, measure the count rate
(counts per minute) for several different thicknesses of aluminum
shielding and use graphical scaling techniques to decide whether the
relationship between count rate and shielding thickness is an
exponential or a power law model. Note that it is important to
plot as you go - use the counting time wisely.LEARNING CATALYTICS QUESTIONS 11-13.
Fitting a Model to the Data
By adjusting a straight line model on your linearized plot,
determine the parameters of the model function that describes your
data.
Marking Scheme
2 marks for background measuremnt and comparison
2 marks for first attenuation measurements and comparison to
background
3 marks for description of your data-taking strategy, adapted as you
work to improve it
4 marks for high-quality data on a linearized plot
2 marks for fit a fit on the linearized plot, and a plot of
residuals
3 marks for conclusion, including model with parameters and comments
on background