Radio Waves
Download and run the PhET Radio Waves and EM Field simulation. Use the simulation to answer the following questions.
- Select the following simulation settings: manual, full field, electric field, and static field. Record your observations.
Move the electron down the antenna. Record your observations.
Move the electron back to its starting position. Change the setting from static field to radiated field. Record your observations.
Move the electron down the antenna. Record your observations.
Change the simulation settings from manual to oscillate. Record your observations.
Analyze your observations, and draw some conclusions based on this information. Record your conclusions in the last row on the data table.
| Settings | Observations (be specific and detailed) |
| Static field, motionless electron | |
| Static field, move electron down the antenna | |
| Radiated field, motionless electron | |
| Radiated field, move electron down the antenna | |
| Radiated field, oscillating electron | |
| Conclusions | |
- Select the following simulation settings: oscillate, full field, electric field, and radiated field. Switch back and forth between the force on electron setting and the electric field setting. Pay particular attention to the receiving antenna electron. Complete the following table by filling in either up, down, or zero for the directions.
Analyze your observations and draw some conclusions based on the observations. Record your conclusions in the last row on the data table.
| Position of electron in receiving antenna | Direction of force on electron in receiving antenna | Direction of electric field at location of electron in receiving antenna |
| Maximum | ||
| Minimum | ||
| Equilibrium (halfway between max and minimum positions | ||
| Conclusions | ||
- Select the following simulation settings: manual, full field, electric field, and radiated field. Run the simulation long enough so that there are no EM waves on the screen.
Check the box for electron positions. Change the simulation setting from manual to oscillate. Let the simulation run for a bit, and then pause the simulation. Answer the following observation questions:
| Question | Answer |
| Do the transmitting and receiving antenna electrons start moving at the same time? If not, which one moves first? When does the other start to move? | |
| When the transmitting electron is at its maximum position, where is the receiving antenna electron (e.g., max, min, zero, or some other position)? | |
| Compare the time that it takes the transmitting electron to complete one full cycle of motion to the time it takes the receiving electron to complete one full cycle of motion. | |
| Compare the distance the transmitting electron travels in one full cycle to the distance traveled by the receiving electron during one full cycle. |
- Use your observations in tables 1, 2, and 3 to explain the motion of the electron in the receiving antenna. What causes it to move? Why does it change direction? How is this motion related to the electron in the broadcasting antenna? Be specific and detailed. Use your observations to support your discussion.
5.Select the following simulation settings: oscillate, full field, electric field, and radiated field. Let the simulation run long enough for the receiving antenna electron to begin oscillating. Pause the simulation. Take a screen shot. Paste the screen shot into the space below.
Answer the following observation questions based on the above picture.
| Observation question | Answer |
| Roughly, how many electric waves are present in the above picture? | |
| How could you use this electric field diagram to determine the length of the electric waves? |
- Change the setting from full field to curve with vectors. Switch back and forth between force on electron and electric field settings. What does the curved line in the curve with vectors setting represent? Explain your reasoning.
7.Select the following simulation settings: oscillate, curve with vectors, electric field, and radiated field. Make the following changes, and observe the effect the change has on the wavelength, frequency, and amplitude. Also, observe how this change affects the behavior of the motion of both the transmitting and receiving electrons.
Reset the simulation between each system change (e.g., set the frequency back to its original position before changing the amplitude).
Record your observations.
Analyze your observations, and draw some conclusions based on the observations. Record your conclusions in the last row on the data table.
| System changes | Effect on the wavelength | Effect on number of waves between the antennas | Effect on wave amplitude | Effect on transmitting electron behavior | Effect on receiving electron behavior |
| Increase the frequency | |||||
| Increase the amplitude | |||||
| Conclusions | |||||
Summary and Reflection
Summarize the major findings of this exploration. What do you know now that you did not know before? Be specific.
