Name
Date
Hands-on Investigation: Testing “Everyday” Items for Radioactivity
In this investigation, you will be working with a digital radiation
monitor that contains a GM tube. You will explore how this
monitor works by measuring some of the ionizing radiation in
your classroom. This monitor detects ,  and  radiation.

The window at the front of the monitor is made of mica
and is fragile! Please do not let anything (especially a
pointed object) touch this window.
 For accurate readings of substances with low levels of
radioactivity, the mica window should face the material and
be placed close to the substance in question, without actually Figure 1: Vernier Digital Radiation Monitor.
Image Source: Digital Radiation Monitor manual.
touching the substance.
 Watch your teacher’s demonstration of how to set the
counter to count for 6 minutes using the timed count mode and then set your counter to count
for 6 minutes.
1. Select your first object or substance to be
tested for radioactivity. Set it about 1 cm in
front of the mica window and turn the monitor
ON as described by your teacher. Start your
stopwatch as soon as you activate the monitor
for counting. Keep your stopwatch running
and complete the data table. NOTE: If the
substance to be tested is in a container, the
walls of the container may block some of the
radioactivity so the monitor has to be
positioned in such a way as to measure the
substance directly.
Item or Substance __________________
Time
(min)
Total
Counts
Change in Counts
(from previous value)
0
1
2
3
4
5
6
Since your measurements were made at 1
minute intervals, your Change in Counts column represents the counts per minute
(CPM).
2. Use the data from the table to determine the following:
Min CPM = ________
Max CPM = ________
Avg CPM = ________
3. Now repeat this procedure for two more items or substances you think may be
radioactive.
Item or Substance __________________
Time (min)
Total Counts
CPM
Item or Substance __________________
Time (min)
Total Counts
CPM
0
0
1
1
2
2
3
3
4
4
5
5
6
6
Min CPM = _______ Max CPM = _______
Min CPM = _______ Max CPM = _______
Average CPM = __________
Average CPM = __________
4. Compare your results with other groups. Describe any similarities or differences
you found by comparing the items you tested with items tested by other groups. BE
SPECIFIC.
5. Is there anything that your group or any other group found that you think may be
radioactive? Explain your answer using data you collected.
6. Repeat the procedure one more time and this
time do not put anything in front of the
radiation monitor.
Item or Substance __________________
Time (min)
Total Counts
CPM
0
1
2
3
7. How do these results compare with the items
and substances that have been measured so
far? Do you think any of the items measured
so far are radioactive? Why or why not?
4
5
6
Min CPM = _______ Max CPM = _______
Average CPM = __________
The radioactivity measured by a radiation monitor when nothing is in front of it is called
“background radiation.” When testing for the presence of radioactivity one must always
measure the background radiation first and then subtract it from any radioactivity
measurements recorded.
8. Using this information, now test two more items/substances to see if they are radioactive:
Item or Substance __________________
CPM
Time
Total
CPM Corrected
(min)
Counts
Item or Substance __________________
CPM
Time
Total
CPM
Corrected
(min) Counts
0
0
1
1
2
2
3
3
4
4
5
5
6
6
Min CPM = _______ Max CPM = _______
Min CPM = _______ Max CPM = _______
Average CPM = __________
Average CPM = __________
9. Now test some of the items supplied by your teacher for the presence of radioactivity
using what you have learned so far in this activity.
Item or Substance __________________
CPM
Time
Total
CPM
Corrected
(min)
Counts
Item or Substance __________________
CPM
Time
Total
CPM
Corrected
(min) Counts
0
0
1
1
2
2
3
3
4
4
5
5
6
6
Min CPM = _______ Max CPM = _______
Min CPM = _______ Max CPM = _______
Average CPM = __________
Average CPM = __________
10. Which items tested in this lab activity are emitting radioactivity? Use data to support
EACH of your conclusions.
11. Which items are you uncertain about? Why? Use your data to support your answer.
12. If time allows, determine if several other materials are radioactive. (Your teacher may
have additional data tables OR you can create your own on your own paper.)