The Effects of Distance and Shielding on Exposure to Radiation

Background radiation is the invisible radiation that is always present in our environment. It comes from a variety of sources, both natural and man-made. Natural sources include cosmic rays from space, radiation from rocks and soil, and radon gas.

The amount of background radiation we are exposed to varies depending on location, with some areas having higher levels than others. For example, people who live in areas with high levels of radon gas in the soil are exposed to more background radiation than those who live in areas with lower levels.

This investigation begins with a measure of the background radiation in the laboratory where the measurements are being made. The average background radiation should be calculated and used to adjust measurements taken during both the distance and shielding labs that follow. Background radiation should be subtracted from every radiation measurement to ensure the accuracy and reliability of the results by accounting for the natural radiation that is always present in the environment.

Click here to download the Student Handout for this virtual lab.

Background Radiation

*Click on each video and record the background radiation.*
Trial Number	Count after 30 seconds
1	Background Radiation Count 1
2	Background Radiation Count 2
3	Background Radiation Count 3

How Distance Affects Exposure to Radiation

Click on each video and record the resulting count on the corresponding data table in the student handout. REMEMBER to subtract the Average Background count before recording.

*Click on each video and record each count on the corresponding data table.*
Shelf Position	Beta Count	Alpha Count	Gamma Count
2nd Shelf	Beta Source Shelf 2	Alpha Source Shelf 2	Gamma Source Shelf 2
3rd Shelf	Beta Source Shelf 3	Alpha Source Shelf 3	Gamma Source Shelf 3
4th Shelf	Beta Source Shelf 4	Alpha Source Shelf 4	Gamma Source Shelf 4
5th Shelf	Beta Source Shelf 5	Alpha Source Shelf 5	Gamma Source Shelf 5
6th Shelf	Beta Source Shelf 6	Alpha Source Shelf 6	Gamma Source Shelf 6

How Shielding Affects Exposure to Radiation

Click on each video and record the resulting count on the corresponding data table in the student handout. REMEMBER to subtract the Average Background count before recording.

*Click on each video and record each count on the corresponding data table.*
Shielding Material	Beta Count	Alpha Count	Gamma Count
Count from 2nd shelf NO SHIELDING	Beta Source Shelf 2	Alpha Source Shelf 2	Gamma Source Shelf 2
Notebook paper	Paper Shielding with Beta Source	Paper Shielding with Alpha Source	Paper Shielding with Gamma Source
Plastic - THIN	Thin Plastic Shielding with Beta Source	Thin Plastic Shielding with Alpha Source	Thin Plastic Shielding with Gamma Source
Plastic - THICK	Thick Plastic Shielding with Beta Source	Thick Plastic Shielding with Alpha Source	Thick Plastic Shielding with Gamma Source
Aluminum (Al) - THIN	Thin Aluminum Shielding with Beta Source	Thin Aluminum Shielding with Alpha Source	Thin Aluminum Shielding with Gamma Source
Lead (Pb) - THIN	Thin Lead Shielding with Beta Source	Thin Lead Shielding with Alpha Source	Thin Lead Shielding with Gamma Source
Lead (Pb) - THICK	Thick Lead Shielding with Beta Source	Thick Lead Shielding with Alpha Source	Thick Lead Shielding with Gamma Source

Discussion:

Use the data collected from the tables and the information above to answer the following questions.

Why did we need to first measure background radiation?
Where does background radiation come from?
What happened to the radioactive count as each source was moved farther (lower shelf position) from the detector?
Which source (beta, alpha, or gamma) is most easily shielded?
Which source is the least easily shielded?
Which of the shielding materials was the most effective?
Which of the shielding materials was the least effective?

This lab was created with support from Dr. Nathaniel Lifton at Purdue University with funding from the National Science Foundation grant AGS-2303294 (P4CLIMATE).