University of Virginia
Physics Department

Personal Exposure to Radiation

A Physical Science Activity

2003 Virginia SOLs



Students will

  • differentiate between naturally occurring and manmade radiation;
  • identify different sources of radiation;
  • compare amounts of radiation exposure from a variety of common sources;
  • identify the three forms of basic radiation protection: time, distance, and shielding.

Motivation for Learning

Driving Questions

List the answers as given by students to the following questions on the board or a transparency:

How many useful uses of radiation can you name? (x-rays, food irradiation to eliminate bacteria, smoke alarms, oil discovery, radio waves, TV waves, microwaves, light, etc.).

Can radiation exposure be totally avoided? (no, there is radiation coming from outer space and from material all around us. Our radiation exposure is higher when we fly in airplanes.)

What are some unusual sources of radiation? (smoke alarms, concrete walls, microwaves, TVs)

When is radiation exposure a risk worth taking? (for health reasons: x-rays for teeth and tuberculosis, food irradiation)


Background Information

Every day we are exposed to radiation. Radiation is the process of emitting energy in the form of particles or waves. Some forms of radiation are more energetic (and therefore more potentially harmful) than others. The only difference between different waves of the electromagnetic spectrum is the frequency (or amount of energy) of each wave. X-rays are much more energetic than radio waves. Exposure to energetic waves like x-rays should be limited. However, people permit x-ray radiation exposure in order to locate a broken bone or identify medical problems. Some forms of radiation exposure are unavoidable, such as cosmic radiation from outer space.

The basic unit for measuring radiation received is the rad (roentgen absorbed dose). One rad equals the absorption of 100 ergs (erg--a small but measurable amount of energy) in every gram of tissue exposed to radiation. To show biological risk, rads are converted to rems. The rem (roentgen equivalent man) is adjusted to take into account the type of radiation absorbed and the likelihood of damage from the different types of radiation. Exposures are normally in fractions of a rem, so the commonly used unit of exposure is the millirem (mrem). 1 rem = 1000 millirem. Most scientists estimate that the average person in the United States receives a dose of about 360 millirem of radiation per year.

See the two sites given in the Extensions for considerable additional information about nuclear radiation, reactors, radioactive waste, etc. They have lesson plans for teachers.



Student Activity

To print out the Student Copy only, click here.




  1. Have students list 3 sources of radiation that they think have the most potential danger.
  2. Explain that naturally occurring radiation has always been present. Show the chart that lists types of naturally occurring radiation.
  3. Describe sources of manmade radiation.
  4. Explain the units for radiation exposure: rem and millirem.
  5. Have each student fill in their own activity sheet.
  6. Allow students to compare sources of radiation that they thought were most dangerous to the chart of radiation exposure doses. How does nuclear energy risk compare to other forms of exposure?



Activity Sheet

To print out the Activity Sheet only, click here.


Average Personal Radiation Dose

Every day each of us is exposed to radiation: ultraviolet light from the sun, x-rays, warmth from other people, and a vast spectrum of electromagnetic waves. Some of these are very high energy and potentially dangerous. Exposure to these should be limited. Some radiation exposure is unavoidable, such as the cosmic radiation from space. Some radiation is permitted for medical or health benefits.

Use the information below to calculate your exposure to radiation for the past calendar year. This is only an estimated value.

Type of Radiation

Amount of Radiation in mrem

From Space


Cosmic radiation at sea level - 26


For your elevation (in feet) add:


1000 feet add 2


2000 feet add 5


3000 feet add 9


4000 feet add 15


From the Ground


(for the Atlantic Gulf Coastal Plain)


From Food, Water and Air


From Building Materials


If you live in a wooden structure -5


If you live in a brick structure -7


From Jet Plane Travel


For each 2500 miles add 1


From Nuclear Fuel Plants


Average dose is .1 mrem if there are one or more plants in your state.


Virginia has two nuclear plants.


From Radioactive Waste Disposal


Average US dose is 1.0


From Medical Diagnosis


x-rays: chest - 6


pelvis and hips - 65


arms, hands, legs, feet - 1


skull, head, neck - 20


mammogram - 400


From Cigarette Smoke


If you are exposed to cigarette smoke on a regular basis add 100-500


(Add 500 if you are exposed every day for 8 hours or more)


If you smoke one pack of cigarettes or more a day add 1500







The Enivronmental Protection Agency has a nice site called "Students and Teachers' Radiation Protection Pages" that is full of useful information. It has a quiz similar to the one in this activity. Click here to see it.

The United States Nuclear Regulatory Commission has a teacher lesson site that can be downloaded. It contains the figure that we have in this site. Click here to see it.


Students with Special Needs

Each student should be able to participate in this activity.

Click here for further information on laboratories with students with special needs.



  1. Each student should complete a Personal Radiation Dose worksheet.