RADIATION LAB EXERCISE
Date: _______________
Name(s):_______________ _______________ _______________
_______________ _______________ _______________
Experiment #1
Background Radiation
1. Use a geiger counter to measure the background radiation in counts per
minute (cpm).
Background =
cpm
Where is this radiation coming from? From you? From your teacher?
_________________
Experiment #2
Time and Radiation Exposure
Your Grandfather gave you an old clock that contains radium paint (unknown to him). You place the
clock on your headboard 5 inches from your pillow on your bed. If you leave it there for 1 year (365
days) and we assume that you sleep in your bed 8 hours every night, what will be the radiation dose
to your head after 1 year?
Measure the radiation field at 5 inches from the clock (or substitute item.) Record the value.
_____mR/hr at 5”
Calculate: Radiation Dose (mrem)=365 days/yr x 8 hrs/day sleep x _______mR/hr
(at 5” away from the clock)= _______________ mrem to your head!
Experiment #3
Distance and Radiation Exposure
DISTANCE
RADIATION READING
2 inches
6 inches
12 inches
__ inches
__ inches
1
RADIATION LAB EXERCISE
What effect does distance have on the radiation emitted from the object? Plot results.
Experiment #4 Shielding of Nuclear Radiation
1. Using the geiger counter to measure the radiation at the surface of a radium dial watch (or other
radioactive object.)
___________cpm
2. Place a piece of paper over the radium dial watch and measure the radiation level at the surface
of the radium dial watch through the paper.
___________cpm
3. Place a piece of plastic over the radium dial watch and measure the radiation level at the surface
of the radium dial watch through the plastic.
___________cpm
4. Place a piece of lead or metal over the radium dial watch and measure the radiation level at the
surface of the radium dial watch through the lead.
___________cpm
Question: How did the different types of shielding affect the radiation level?
___________________________________________________________________________
___________________________________________________________________________
Experiment #5 Which Items are Radioactive?
Use a geiger counter and find which items are radioactive on the table and record the results below.
________________________________________________________________________________
________________________________________________________________________________
________________________________________________________________________________
________________________________________________________________________________
________________________________________________________________________________
Extra credit: Which items emit beta radiation, which emit gamma radiation?
________________________________________________________________________________
________________________________________________________________________________
________________________________________________________________________________
________________________________________________________________________________
________________________________________________________________________________
2
RADIATION LAB EXERCISE
Experiment #4a
Shielding of Beta Radiation
1. Position the geiger counter as shown to allow a thin tray of No Salt (KCl) to slide under. Keep the
position the same during the experiment. The detector cover can be removed safely (it unscrews).
2. Count the clicks for 60 seconds with nothing under the detector. This measures background
radiation in counts per minute (cpm). Subtract this reading from all readings (see chart.)
3. Now slide a tray of KCl under the detector (about 1 tablespoon, spread out). The meter dial
should read about 50 cpm (counts per minute). Where is the radiation coming from? Count clicks
for 30 seconds, and multiply by 2. Or do it twice, and add the counts to get cpm.
4. Now slide squares of aluminum foil between the detector and KCl. Don't move the detector.
Repeat the counting, adding one foil each time. The chart below will help collect the data. Use
10-12 squares of regular foil or 8-10 squares of heavy duty foil. Cover all the salt.
Set-up:
Tape down to table.
Counts/30sec
st
nd
2
1
cpm
cpm-minus
background
5. Plot the results (columns 4 & 5). Draw a
straight line through the data, or fit the data
to a linear equation. What is the slope of the
line? Each foil stops some beta rays. How
many layers are needed to stop half?
If 0.3 mm of Al will stop half, how thick is the foil?
A physicist uses this experiment to determine
the energy of the beta rays.
KCl
Foil
layers
0
1
2
3
4
5
6
7
8
9
10
11
12
3