15.3 Producing EMR

Electromagnetic waves were first produced and detected in 1887, shortly after Maxwell's death.  German physicist Heinrich Hertz (1857-1894) used a spark gap to rapidly move an electric charge back and forth producing a wave of 10 ⁹ Hz, which was detected by a nearby antenna.  He was also able to confirm that the waves travelled at nearly 3.0 × 10 ⁸ m/s.  Hertz called these electromagnetic waves "radio" waves.  For his significant contribution to the study of science, the SI unit of frequency Hertz, or Hz (cycles per second or seconds ^-1 ), was named in his honour.  Today, radio waves are very common. AM/FM radios, cellphones, garage-door openers, and cordless telephones operate in the radio range of the spectrum.  You will explore how they are produced, transmitted, and received using your own radio station.

 

Use the Radio Waves simulation to open your own radio station. (Note: You many need to use Firefox.)

 

Your radio station has a transmitting tower that consists of an electron in a long conductor.  Your listening audience is in the small house with a receiver attached to a long conducting antenna.

 

Select "Manual" on the Transmitter Movement menu and wiggle the electron in the transmission tower.  Observe the correlation to the wave that is produced.  Next, select "Oscillate" and observe the simple harmonic motion of the electron.

 

 

Self-Check Answer the following self-check questions then click the "Check your work" bar to assess your responses.

 

SC 4. 

Does the frequency of the simple harmonic motion match the frequency of the radio wave?

 

SC 5. 

What causes the electron to accelerate up and down in a real transmission antenna?  Explain how this will be related to the frequency of the radio wave produced.

 

SC 6.  

Describe the relationship of the direction of the electric wave, the magnetic wave, and the direction of the EMR.