In-class activities

Electromagnetic waves

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.

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?

Black Body Radiation
Link to simulation of Black Body radiation https://phet.colorado.edu/sims/blackbody-spectrum/blackbody-spectrum_en.html

• Play with the simulation.
  Change the temperature.  Can you find a temperature which emits primarily in the visible?
  Why aren't incandescent light bulbs efficient?
  Which is hotter, a flame which looks blue or a flame which looks red?
  

The Photoelectric Effect

Link to simulation of the photoelectric effect https://phet.colorado.edu/en/simulation/photoelectric

• Play with the simulation.
  Ramp up the intensity.  Does it emit electrons at all wavelengths?
  Set the voltage to be negative.  What happens?  Try changing the wavelength and the intensity.
  What would happen classically?
  Can you calculate the work function for a metal?  How does this compare to the true value?
  

• You can elect Show photons in the Options menu to show the light beam as composed of individual photons.

• You can select Control photon number instead of intensity in the Options menu to change the Intensity slider to a Number of photons slider.

• You can use the camera icon to take a snapshot of the graphs so that you can compare graphs for different settings.

• You can Pause the simulation and then use Step to incrementally analyze.