Name: _______________________________
Period: ___
Diffraction & Interference Computer Lab
Date:_________
Purpose: To take a closer look at what we’ve learned this week, and see it in a different light. All the web
links can be accessed through the course web page:
http://www.glenbardwesths.org/teachers/Szarzak/SzarzakConceptualPhysics.html
Start by going to the following web site. (The links are also posted on Mr. Szarzak’s homepage)
http://micro.magnet.fsu.edu/primer/java/diffraction/basicdiffraction/index.html
Once the JAVA application loads, you can change the wavelength of light and the size of the aperture. Make a
few changes here until you get the hang of it, and then answer the following questions. On occasion, the
application may stall out for a few seconds, be patient.
1) What are the wavelengths for the 3 primary colors (red/green/blue)?
2) Describe how changing the wavelength of the light affects how the light spreads beyond the single slit.
What is the relationship between wavelength and diffraction?
3) Set the wavelength to a value near 500nm. Now change the size of the aperture to different values. What
is the relationship between the size of the aperture and the diffraction?
4) Try a number of combinations where the aperture is about double the wavelength. Do you notice
anything constant about the diffraction, or a trend? (This is not a yes/no question – explain what is
constant, or what the trend is.)
5) Set both values to their minimum values. Notice that they are about the same. As you increase the
wavelength, the aperture will also increase at about the same rate. From what you’ve seen so far, what
would happen if the aperture were less than the wavelength?
Now go to this web site: (Remember, the links are posted on Mr. Szarzak’s homepage)
http://micro.magnet.fsu.edu/primer/java/particleorwave/diffraction/index.html
Once the JAVA application loads, you can move the slider bar to change whether light behaves as a particle, a
wave, or a combination of both. Be sure to try moving the gray barrier as well. On occasion, the application
may stall out for a few seconds, be patient. Make your observations and then answer the questions below.
6) Adjust the slider on the Java applet to explain how light would move past a barrier if it behaved strictly
as a particle. Try moving the gray barrier to make the behavior more apparent.
7) Adjust the slider on the Java applet to explain how light would move past a barrier if it behaved strictly
as a wave. Try moving the gray barrier to make the behavior more apparent.
8) What light phenomenon have we discussed that supports the theory that light behaves like a wave? How
have your experiments with the Java applet supported this?
9) Draw a sketch of what light waves with one wavelength (all one color) would do when passing through
a single slit. Hint: Scroll down the page!
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Go to this web site: (Remember, the links are posted on Mr. Szarzak’s homepage)
http://lectureonline.cl.msu.edu/~mmp/applist/Spectrum/s.htm
You can move the vertical blue line to learn more about each wavelength.
10) List 5 types of EM radiation, in order from lowest energy to highest energy. WARNING: PAY
ATTENTION TO THE ENERGY VALUES IN SCIENTIFIC NOTATION FROM LEFT TO RIGHT.
11) Pick two different EM radiations. Multiply the frequency (in Hz) of the first one by its wavelength (in
meters). Now multiply the frequency (in Hz) of the other radiation by its wavelength (in meters). Show
both of your calculations. Don’t forget units.
12) Write your answers to #11 rounded to 1 significant figure. How do the two results compare? What does
this value represent?
13) Compare the energy it takes to produce red light vs. blue light. Using the left and right arrow keys will
help. Which requires more energy, and how many times more?
14) What type of EM radiation has a wavelength of 1m?
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Go to this site: (Remember, the links are posted on Mr. Szarzak’s homepage)
http://lectureonline.cl.msu.edu/~mmp/kap24/polarizers/Polarizer.htm
The demo shows polarization. First select the number of polarizers to 1. Move the slider to adjust the angle of
the polarizer. Make note of what percentage of the emitted light is allowed to pass through one polarizing filter.
Select the button for 2 polarizers. You can change the angles of both filters and observe the resulting EM
radiation.
15) How must the two filters be oriented in order for the maximum light to pass through?
CIRCLE ONE:
Perpendicular
Parallel
Somewhere in between
16) If the first filter is at 40, how many angles will allow the maximum light to pass, and what are they?
17) Set the first filter to 10o. How many angles block all of the light? What are these angles?
Select the button for 3 polarizers. Set all the angles to 0o. Note how much light passes through the filters. Now
rotate polarizer 3 to 90o, making it perpendicular to polarizer 1. Notice how much light is now allowed to pass
through the filters.
18) Rotate polarizer 2. What do you observe when the angle of polarizer 2 is different than both polarizers 1
and 3?
19) What is the maximum percentage of light that is allowed to pass when polarizer 2 is rotated? What
angle is polarizer 2 oriented to allow the maximum amount of light to pass through the three filters?
20) Make sure the polarizers are set to 0o, 45o, and 90o, respectively. Set the number of polarizers to ‘1’,
then ‘2’, and then ‘3’. What trend do you observe in the percentage of light that is allowed to pass
through the polarizers as you change from 1 to 2 to 3 filters?
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