How to Make RF Waves Visible

Cell phones use radio frequency waves.

Radio frequency waves are a mode of communication for wireless technologies, such as cordless phones, radar, GPS and radio broadcasts. RF waves are affected by the Doppler effect, which causes a shift in the wavelength of light emitted by a moving object. Computers can make RF waves visible by converting Doppler shift data about the reflected radio waves into pictures. Weather forecasters use pictures of wind motions to help them understand weather patterns. According to "USA Today," a computer that is a part of Doppler radar uses wave frequency changes to show directions and speeds of winds blowing around other objects. Police radar also utilizes radio waves and makes use of the Doppler effect to measure the speed of vehicles.

Things You'll Need

• Handheld radar gun

Instructions

1. Purchase a handheld radar gun to check the speed of approaching vehicles. Radar guns use Doppler radar to measure speed by looking for a red shift or blue shift in light, according to PBElectronics.com. This is similar to how astronomers measure the distance of stars with a telescope.

2. Avoid moving while using the radar gun. Any movement can cause unpredictable results. Radar can also be influenced by electromagnetic and physical phenomena. For instance, radar will pick up interference from power lines and air conditioning units. Some forms of interference will disappear when the radar detects a moving object.

3. Position yourself so that the approaching car is moving in your direction. The faster a car is traveling, the greater the change in the radar frequency waves it reflects. The radar gun detects the frequency of the returned waves.

4. Point the radar gun at an approaching vehicle. As the vehicle approaches, the radar gun (or transmitter) emits radio waves that bounce back toward the radar gun. The antenna of the radar gun emits a beam of light in the radio frequency range. Light bounces off the targeted car or truck and returns to the radar antenna.

5. Look at the radar unit display. According to the Curiosity Discovery website, the radar gun's computer calculates the vehicle's speed by figuring the difference between the frequency emitted and the frequency reflected. Locate the target speed number, which is the speed of the moving object.

References

• Wavelength Shift for Moving Objects
• USA Today: Doppler Radar Is a Key Forecasting Tool

Resources

• Nationalatlas.gov: What Is AVHRR?
• Doppler Shift: Red and Blue Shifts
• Physics Planet: Doppler Effect