In-class activity

Electromagnetic radiation is produced by accelerating charges.  When charges are exposed to electromagnetic radiation, they experience a force and accelerate.  Explore this interaction with radio waves using an on-line simulation from the University of Colorado PhET group. 
Link to the simulation: http://phet.colorado.edu/en/simulation/radio-waves  Click "Run Now!" or download and then open it.

(a)  Explore the interface!  Click Help to make sure you are aware of all controls.

• Play with the simulation.
  In manual mode try to move the electron with constant velocity.  What happens?
  Make the electron start and stop rapidly.  What happens?
  How is the radiation field produced?
  How is it detected?

(b)  Use the simulation to decide which of the following statements is true.

• (1)  If the oscillation frequency of the transmitting electron decreases, the oscillation frequency of the electron in the receiver is instantaneously affected.
  (2)  The electron in the receiving antenna oscillates at a lower frequency than the electron in the transmitting antenna because of the distance between the antennas.
  (3)  If the frequency of the transmitting electron decreases by a factor of two, it will now take longer for the electromagnetic signal to reach the receiving antenna.
  (4)  If the frequency decreases, the wavelength decreases.