Now, select the Slits simulation at the bottom of the screen and choose Light (red) for the type of wave, as before. Also, make sure there is a barrier with one slit and use the tape measure as well as the slider bar below the slit to place it roughly 1290 nm away from the light source. Adjust the slit width to 300 nm. Finally, select the start button at the source location to begin producing the waves.
Which statement best describes how the intensity of the wave depends on position along the screen? Selecting the Intensity checkbox will show a plot of the intensity on the screen.
a) The intensity is large near the middle of the screen, then decreases to nearly zero, and then increases again as the distance from the middle of the screen increases.
b) The intensity is a maximum near the middle of the screen (directly to the right of the source) and significantly decreases above and below the middle of the screen.
c) The intensity is roughly constant.
Learning Goal:
To understand the cause of constructive and destructive interference for the double-slit experiment, and to explain how the interference pattern depends on the parameters of the emitted waves.
For this tutorial, use the PhET simulation Wave Interference. This simulation allows you to send waves through various barriers and observe the resulting interference patterns.
Start the simulation. You will see three possible selections: Waves, Interference, and Slits. To switch between simulations at any point, select the desired simulation on the toolbar located at the bottom of the screen. In these simulations, you can choose between water waves, sound waves, and light. You can adjust the slit width and slit separation using slider bars, and you can place a barrier containing one or two slits in front of the source of the waves. There are also several measuring tools at the upper-right hand corner of the screen, including a detector that produces plots showing the wave amplitude vs. time for the location of the two sensors on the detector, which can be dragged to a different location.
Feel free to experiment with all of the simulations to get a feel for how they work. When you are done, and before starting Part A, set the simulation to Waves and select the Reset Icon.