Geiger Counter Experiment #3
Radioactive Decay Experiment Using TV Screen Dust
< Back To Experiment 2 | Forward To Experiment 4 >
The dust wiped from the front of a television screen is radioactive.
Every cubic meter of air contains a certain number of dust particles
and radon atoms. Radon is radioactive and does not bond with
other atoms. When Radon decays, it becomes an atom of polonium
with a + charge. The polonium is attracted to any nearby particle
of dust and will quickly attach itself. The polonium-dust still
retains its + charge and is attracted to the negatively electrostatic
charged surface of a CRT screen or old style TV screen. This is why the old CRT style TV screen dust always
appears to be more radioactive than other dust.
The dust contains short-lived radon-222 decay products (polonium-218, lead-214, bismuth-214, and polonium-214). The radioactivity is due to these radioactive decay products attached to tiny dust particles.
Wipe the front of a CRT screen or old style TV screen with a Q-tip or tissue paper dampened with rubbing alcohol, collecting as much dust as possible.
Bring the sample as close as possible to the GM tube of the Digital Geiger Counter. Using the graphing program you can record the radioactive decay.
Alternatively, you can collect dust from the filter of an air cleaner although the dust collected from this source may not be as radioactive.
The chart below shows the radioactive decay using a one hour time base.
Chart of Radioactive Decay of TV Screen Dust
Partical Decay Sequence of Radon
Radon-222 alpha decay --> Polonium-218, half life 3.8 days
Polonium-218 alpha decay --> Lead-214 half life 3 minutes
Lead-214 beta decay --> Bismuth-214 half life 20 minutes
Bismuth-214 beta decay --> Polonium-214 half life 200 microseconds
Reference 1: Why does my TV collect radioactive dust?
Reference 2: Radioactive TV screen dust
Back to Top