Part 1. Wave Interference Simulation
Open the PhET Wave Interference Lab: https://phet.colorado.edu/sims/html/wave-interference/latest/wave-interference_en.html
1. Go to Waves.
a. Click on “light” and then show “graph” and “screen”.
Click on the green button on the laser pointer. Draw how the light waves look as they approach the screen. Then draw
how the light actually appears on the screen below. NOTICE that the amplitude of the light wave is decreasing as it
spreads out, this is called “damping” of the wave.
 screen
2. Go back to the URL and restart. Click on Interference. Click on “light” and then show “graph” and “screen”.
a.
Turn on both lights. How does turning on both lights change the behavior (shape) of the wave? How did the
light waves appear on the screen?
 screen
b. If you increase the separation between the two lasers, what happens to the spacing, bright center and the
dark bands to each side. The measuring tape tool can help you measure.
c.
If you increase the frequency of the light which would move it towards blue, you will decrease the wavelength.
What happens to the spacing when you do this?
d. Using what you learned during the direct instruction, explain why there are black lines and green lines on the
screen.
3. Go back to the URL and restart. Click on Slit. Click on “light” and then show “graph” and “screen” and “intensity” and
change from one slit to two slits
a. What do you observe happening on the screen?
 screen
b. Increase the slit separation and describe how it changes the pattern of light on the screen.
c.
Now increase the frequency, thereby decreasing the wavelength of the light. What changes in the pattern
when you do this?
d. Increase the Slit Width. What effect does changing this have on the diffraction pattern?