Single Slit Lab

(this experiment is to be used with the Waves lab from SPECS)

Waves play such an important role in our lives and most of us very rarely pay any attention to them. Without waves we would know very little about the world around us. Sound and light are waves, in fact all electromagnetic radiation are waves. These electromagnetic radiation include radio waves, microwaves, visible light, x-rays and so on. Therefore, the more you know about waves the more you know about the world around you.

Many natural phenomena occur around us that can be explained very nicely with an understanding of vibrations and waves. There are things around us that appear to be rigid but actually vibrate (i.e.. buildings, bridges, antennas). If you are a engineer or architect you must be very familiar with how these vibrations affect the design and construction of these structures.


The purpose of this activity is to give you the chance to "see" and explore the interaction of waves. In your everyday life you have probably experienced this type of interaction many times. This activity will allow you to control the interaction and help you to visualize what happens. How does the interaction effect the way you view your surroundings?


Words you should know

amplitude, constructive interference, destructive interference, diffraction, frequency, fundamental frequency, index of refraction, phase angle, and superposition.

glossary of terms
Background on light

The search for an understanding of light has been going on for a very long time. Over the centuries it has been thought to travel in tiny particles or corpuscles from the eye to the object and back. Newton used this idea to help explain reflection and refraction. In 1670 Christian Huygens proposed that light was wave like. Then in 1801 Thomas Young showed how light beams can interfere with each other. James Clerk Maxwell in 1865 found that electromagnetic waves travel at the speed of light. Then along came Max Planck who introduced the idea of the quantization of electromagnetic radiation. Today's scientists view light as having both a wave-like or particle-like nature. It depends on how you look at it. You will be looking at light and other electromagnetic radiation from a wave model point of view.

Single Slit


 Step 1: Create two walls of width 15 and height 100. Place the top "wall" at 174, 100, and the bottom "wall" at 174, 250. Set the frequency to 40. Set Index of Refraction to 0 for both.

 Step 2: Place the dotted line so that it is directly between the top and bottom wall.

 Step 3: Run the program. When the first wave front reaches the far wall of the window click on the copy button, located in the graphWindow. Now click on the stop button.

 Step 4: Click the recycle button, this will clear the wave fronts. Do not clear the graph line.

 Step 5: Now change the distance between the walls (in increments of at least 50), and run the program. Make sure you move the dotted line to be directly between the two walls. Again, stop the run when the front wave reaches the far wall. Make a copy of the graph.

Record any changes and their effect on the graph and the waves. What could be responsible for the changes? Explain.

 Step 6: Change the distance again and compare the behavior of the wave and graph with the previous run.

What has changed? What would account for these changes?

 Step 7: Do not clear graphs. Now change your walls to be ovals. Set the ovals to the same locations as the walls and run the program.

Record your observations. Are the graphs the same as they were for the walls? What could account for any of the differences in the graphs? Explain.

Going further: Change the ovals to lenses and repeat your observations. Now you can set the left and right angles, these angles can be positive or negative. Note in this case you are not using lens but walls with curved sides, because the index of refraction is set at 0.

 How is this different than using ovals or walls? What would happen if the index of refraction was not 0?


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