Physics 107 - Making Comparisons
- How to use mean and standard
deviation when comparing data
- Scatter plots in a spreadsheet
Part I - Radiation Count Rate
You will be measuring the rate at which radioactive particles are
measured close to an alpha-emitter. The radioactive particles are
emitted randomly, so you will need to use the statistical
techniques learned so far to come up with a measurement of the
average count rate (in counts/minute) and the uncertainty in that
- Sign out one of the radioactive sources and place it
source-side up (the black material pointing up) beneath the
- Geiger counter height should be set at 2.0 cm
- Spend 10 minutes with others at your lab bench,
discussing what measurements to take in a strictly limited
data-taking session of 20 minutes
- Spend 15 minutes analyzing your data to determine the
average counts per minute, and uncertainty in this average
- Do not touch the apparatus any further - you will need
to remeasure again at the end of the lab period.
Remeasure the pendulum period at angles from 5 to 25 degrees. Spend
5 minutes discussing what measurements to take in a limited period
of 25 minutes You must ensure that you achieve at least 0.1%
precision in the period in order to look for a small effect. Compare
different angles by calculating t-values for different pairs of
angles. Is there a significant angle-dependence?
Plot a scatter plot of the period (y-axis) versus angle (x-axis).
Remeasure the decay rate of the radioactive source. Are the counts
per minute different than they were at the beginning of the lab
1 mark for writing down a plan for 20 minutes of data-taking.
3 marks for measuring the radiation count rate (including
histogram, mean, standard deviation, and uncertainty in the mean).
1 mark for writing down a plan to re-measure pendulum periods in
3 marks for high-precision measurments of pendulum period,
including t-comparisons of different angles
2 marks for scatter plot of period versus angle
3 marks for second measurement of count rate and analysis
1 mark for conclusion on whether the count rate has become smaller