Wave Blockers
| Difficulty | |
| Time Required | Very Short (≤ 1 day) |
| Prerequisites | None |
| Material Availability | Readily available |
| Cost | Low ($20 - $50) |
| Safety | No issues |
Abstract
What do the radio, TV, radio controlled cars, and cell phones all have in common? They all use invisible waves to transmit information. Find out which materials block radio waves, and which materials allow radio waves to pass through by doing this experiment.Objective
In this experiment you will test different materials to see if they block radio waves.
Credits
This project was adapted from a student project submitted to the Marin County Science Fair in California.
Sara Agee, Ph.D., Science Buddies
Share your story with Science Buddies!
I Did This Project!
Please log in and let us know how things went.
Last edit date: 2012-12-07
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 and Concepts
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.
Share your story with Science Buddies!
I Did This Project!
Please log in and let us know how things went.
Experimental Procedure
- 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.
- Attempt to operate the RC car using the remote control. Does it work?
- 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... - Divide the materials into good and bad transmitters based upon your results.
Share your story with Science Buddies!
I Did This Project!
Please log in and let us know how things went.
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?
Share your story with Science Buddies!
I Did This Project!
Please log in and let us know how things went.
Ask an Expert
The Ask an Expert Forum is intended to be a place where students can go to find answers to science questions that they have been unable to find using other resources. If you have specific questions about your science fair project or science fair, our team of volunteer scientists can help. Our Experts won't do the work for you, but they will make suggestions, offer guidance, and help you troubleshoot.Ask an Expert
Related Links
If you like this project, you might enjoy exploring these related careers:
Materials Scientist and Engineer
What makes it possible to create high-technology objects like computers and sports gear? It's the materials inside those products. Materials scientists and engineers develop materials, like metals, ceramics, polymers, and composites, that other engineers need for their designs. Materials scientists and engineers think atomically (meaning they understand things at the nanoscale level), but they design microscopically (at the level of a microscope), and their materials are used macroscopically (at the level the eye can see). From heat shields in space, prosthetic limbs, semiconductors, and sunscreens to snowboards, race cars, hard drives, and baking dishes, materials scientists and engineers make the materials that make life better. Read more
Electrical & Electronics Engineer
Just as a potter forms clay, or a steel worker molds molten steel, electrical and electronics engineers gather and shape electricity and use it to make products that transmit power or transmit information. Electrical and electronics engineers may specialize in one of the millions of products that make or use electricity, like cell phones, electric motors, microwaves, medical instruments, airline navigation system, or handheld games. Read more
