52. DETECTING RADIATION

SUBJECT: Science
GRADE: 7,8,9
GROUP SIZE: Large
TIME: 60 minutes
TYPE OF ACTIVITY: Teacher Demonstration
TEACHING STRATEGY: Guided Discovery Discussion
CONCEPTS: Radiation Detection Radiometer
SKILLS: Observation Inference Interpreting Data
Objectives: To understand that radium can be detected; to understand that satellites use radium detecting devices.

radioactivity detection apparatus diagram

Materials: Test tube; small cork; small nail; paper clip; aluminum foil strips; alcohol; glue.
Teacher Background Information: Since radiation is so harmful to humans, unmanned NASA satellites are being used in space to detect the amount of radiation present. The following activity should help students to understand the necessity for detecting radiation and one type of instrument included on many radiation-studying satellites.
Procedure:

Before class, push the nail and paper clip through the cork together. Take aluminum gum wrapper and cut in half, lengthwise (1/2″ x 3″). Soak strips in alcohol to dissolve glue and peel off paper backing.

Assemble as illustrated: nail, cork, paper clip – touching nail, test tube; aluminum foil – glued onto paper clip.

With the class assembled, demonstrate the presence of radioactivity by taking a comb and rubbing it on some wool and touching it to the nail sticking out of the test tube. Have students note what happens to the foil leaves.

  • What causes the static electricity? (Rubbing the comb on wool generates static electricity, covering the comb with extra electrons.)
  • When the comb is touch to the nail, what happens? (Electrons are transferred down the nail to the foil leaves)
  • Why do the foil halves push away from each other and spread apart? (Because equal charges repel – in this case, negative and negative.)

You can cause the leaves to collapse again by removing the negative charge. This is demonstrated by rubbing a glass rod on a polyethylene plastic bag and touching the nail with the rod. The rod will have been charged positive by removal of electrons. Talk with the students about why the leaves went back together. Make sure they understand that the removal of electrons causes a positive charge and the leaves go back because fewer electrons are present.

Radiation can also cause electrons to be removed. To demonstrate the removal of electrons through radiation, set up the demonstration again but, after the leaves have separated, wait a period of time. The students will see that the halves will collapse on their own. This is a result, in part, of cosmic rays streaming through the jar, ionizing some of the air, discharging the foil. The collapse speed is a measure of the number of cosmic rays entering the jar.

Explain to the students that this type of instrument has been included on many of the radiation-studying satellites.

Through discussion and/or reading, find more complete answers to some of the following questions:

  1. What is radioactivity or when is an atom radioactive?
  2. What is a cosmic ray? How fast does it travel?
  3. What results would you expect if a solar storm were to erupt on the Sun? Can solar storms be predicted? Why would we want them to be?
  4. What is ionization

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