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Project Summary

Difficulty	2
Time required	Very Short (a day or less)
Prerequisites	None
Material Availability	Readily available
Cost	Low ($20 - $50)
Safety	No issues

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Abstract

Objective

In this experiment you will test different materials to see if they block radio waves.

Introduction

What do the radio, TV, radio controlled cars, and cell phones all have in common? They all use invisible waves to transmit information. These waves, called radio waves, are a type of electromagnetic radiation. Radio waves are not harmful, in fact they are an extremely useful method of global communication. Two essential components for this type of communication are a transmitter and a receiver (PBS, 1998):

• Transmitting Antenna (transmitter) - A radio signal from a device travels to the transmitting antenna. The signal creates a corresponding electromagnetic field called a radio wave. This radio wave moves outward in all directions from the transmitting antenna.
• Receiving Antenna (receiver) - A receiving antenna picks up the the radio wave. If the receiving antenna is far away from the transmitter, the signal is very weak.

The ability of a wave to travel through a material is called transmittance, and materials can be divided into good transmitters and poor transmitters. One very good transmitting material for radio waves is the air in our lower atmosphere, which is why radio waves can be transmitted through the air over very long distances. One poor transmitter is the ionosphere of the earth, the uppermost layer of the earth's atmosphere which contains high energy, ionized radiation from the sun. Radio waves that are reflected by our ionosphere stay within the inner atmosphere of the earth. This phenomenon is what makes radio waves so great for global communications, because radio wave signals stay close to the surface of the earth:

This figure shows how the upper layers of the earth's ionosphere (composed of the D, E and F layers) reflect and propagate radio waves transmitted from an AM radio antenna. (image © 2007, Thompson Higher Education)

Like the earth's ionosphere, being a poor transmitter is not always a bad thing. Materials which are poor transmitters are sometimes useful because they can block radio waves from moving through them and become insulators. One way to test different materials is to use a radio controlled (RC) car. You will wrap the receiving antennae of the RC car with different materials to find out which materials block radio waves, and which materials allow radio waves to pass through. Which materials make good or bad transmitters?

Terms, Concepts and Questions to Start Background Research

To do this type of experiment you should know what the following terms mean. Have an adult help you search the Internet, or take you to your local library to find out more!

• Radio waves
• Electromagnetic waves
• Transmission
• Transmitter or tansmitting antenna
• Receiver or receiving antenna
• Ionosphere

• How are radio waves transmitted and received?
• Which materials block radio waves?
• Which materials allow transmission of radio waves?

Bibliography

• Read this tutorial on the transmission of radio waves, or if you have Shockwave you can try the Radio Transmission Activity from PBS:
  PBS, 1998. "A Science Odyssey: You Try It: Radio Transmission," PBS Online, WGBH: Boston, MA. [accessed June 6, 2007] http://www.pbs.org/wgbh/aso/tryit/radio/#
• You can read about radio waves in this Wikipedia article:
  Wikipedia contributors, n.d. "Radio waves," Wikipedia, The Free Encyclopedia. [accessed June 6, 2007] http://en.wikipedia.org/w/index.php?title=Radio_waves&oldid=162535596
• Here is a brief discussion about the transmittance of radio waves vs. light waves:
  NEWTON, n.d. "Ask A Scientist: Radio Wave Transmittance," NEWTON Ask a Scientist Program, Argonne National Laboratory, Division of Educational Programs, Chicago, IL. [accessed June 6, 2007] http://www.newton.dep.anl.gov/askasci/phy99/phy99245.htm

Materials and Equipment

• Radio controlled (RC) Car and controller (both with fresh batteries!)
• Different materials to test:
  • Aluminum foil
  • Plastic wrap
  • Paper
  • Wax paper
  • Cotton
  • Rubber gloves
• A wide open space to test drive your RC car.

Experimental Procedure

1. Wrap the antenna of the RC car and of the receiver in the first material you want to test, using several layers so that they are completely and securely covered.
2. Attempt to operate the RC car using the remote control. Does it work?
3. Repeat this process for each different material, collecting data in a data table:

   Name of Material	Does the Car Work? (Y/N)	My Observations:
   Aluminum Foil
   Cotton
   Paper
   Etc...

4. Divide the materials into good and bad transmitters based upon your results.

Variations

• Use a stop watch to time your test drive over a set distance. Compare the average time for cars wrapped in different materials. Do some go faster or slower? What might this tell you about the transmission of the radio signal?
• You can do a similar experiment using other remote control devices, like your TV or stereo remote. How do different devices respond? Do you think they use similar or different types of waves?
• For an advanced project, try broadcasting different frequencies from an old HAM radio. Wrap a receiver with different materials and compare transmittance at different frequencies. Do different frequencies pass through better than others?

• For more science project ideas in this area of science, see Materials Science Project Ideas.

Credits

This project was adapted from a student project submitted to the Marin County Science Fair in California.

Sara Agee, Ph.D., Science Buddies

Last edit date: 2007-10-17 22:00:00

Career Focus

If you like this project, you might enjoy exploring careers in Materials Science.

Industrial Engineer You’ve probably heard the expression “build a better mousetrap.” Industrial engineers are the people who figure out how to do things better. They find ways that are smarter, faster, safer, and easier, so that companies become more efficient, productive, and profitable, and employees have work environments that are safer and more rewarding. You might think from their name that industrial engineers just work for big manufacturing companies, but they are employed in a wide range of industries, including the service, entertainment, shipping, and healthcare fields. For example, nobody likes to wait in a long line to get on a roller coaster ride, or to get admitted to the hospital. Industrial engineers tell companies how to shorten these processes. They try to make life and products better—finding ways to do more with less is their motto.

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