OpenStax-CNX module: m32280
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Applets for Light and Waves
∗
Nathan Belcher
This work is produced by OpenStax-CNX and licensed under the
Creative Commons Attribution License 3.0
†
Abstract
Applets are web-based Java applications that allow interaction with physical phenomena and help with
visualization of the underlying concepts.
Many examples exist on the web, and this module highlights
four examples and some pros and cons for using the applets in a classroom setting.
1 What is an applet?
According to Sun Microsystems, an applet is a program written in the Java programming language that
can be included in an HTML page, much in the same way an image is included in a page (Sun Mi1
crosystems, http://java.sun.com/applets/
).
Applets provide interactive features as web applications,
because they can capture mouse input (such as rotating or moving objects) and have controls (such as
buttons or check boxes).
Through the user's actions, the applet changes the provided graphic content,
and this makes applets well suited for demonstration, visualization, and teaching purposes (Wikipedia,
http://en.wikipedia.org/wiki/Java_Applet
2
).
For those who may not have any experience with applets and found the above paragraph confusing, an
applet is simply a graphical way on a computer to manipulate variables in an experiment. By changing the
independent variable(s), the dependent variable(s) act as if they would when performing the same experiment
in real life. For example, waves have variables of amplitude, wavelength, frequency, and velocity. An applet
would model this visually, and changing any of these variables will provide eects of the change on the
wave. Applets are also capable of modeling very simple to very complex processes, and by manipulating the
variables students may learn how one variable may aect the entire process.
For students that are not very familiar with physics concepts and cannot visualize the underlying processes, applets are a useful tool in providing the students with concrete examples of a process. Because they
are highly manipulative activities, the applets engage students to change as much or as little as necessary to
understand the concept in a way that is cost- and time-ecient. In addition, while there are many websites
that provide applets for many dierent physics concepts, this module will focus on applets related to light
and waves and provide some examples of both complex and simple applets.
2 How to Get Started With Applets
The major hurdle with incorporating applets into a teaching station is ensuring the computer may run the
Java Runtime Environment. This is easy to do, fortunately, by visiting the Sun Microsystems website about
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Java applets (http://java.sun.com/applets/
Version 1.2: Oct 25, 2009 1:39 pm -0500
http://creativecommons.org/licenses/by/3.0/
1 http://java.sun.com/applets/
2 http://en.wikipedia.org/wiki/Java_Applet
3 http://java.sun.com/applets/
∗
†
http://cnx.org/content/m32280/1.2/
).
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Figure 1
By clicking on the Java Plugin link, Sun provides many ways to download Java for use on local computers.
In reality, most computers that are new have some Java Plugin installed, but as new technology becomes
available it is wise to check the capabilities of your system.
For those more experienced with computer programming, there are many ways to develop your own
applets. Sun Microsystems has a complete Developer Network in which people create their own applets in
many dierent elds, and this website also has a link for educators (middle box right side under Want to
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Learn Java Technology? http://java.sun.com/index.jsp
). In addition, existing applets may be modied
through the source code to perform dierent functions.
Finally, a good way to nd relatively simple applets is through a search engine. By simply typing the
keywords physics applet will give 628,000 results (in Google), and this is a good place to start searching for
applets that t the curriculum. While not all applets are created equal, at least there are ideas to narrow the
search focus and nd the right applet for the occasion. Here are a few websites that contain applets across
many grade levels and science elds, and can also serve as a starting point (further details are provided later
in this module for some of the applet sites):
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Explore Learning: http://www.explorelearning.com
/
Paul Falstad: http://www.falstad.com/mathphysics.html
4 http://java.sun.com/index.jsp
5 http://www.explorelearning.com/
6 http://www.falstad.com/mathphysics.html
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Michael Fowler: http://galileoandeinstein.physics.virginia.edu/more_stu/Applets/
Walter Fendt: http://www.walter-fendt.de/ph14e/
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Edinformatics (compilation of applets site): http://www.edinformatics.com/il/il_physics.htm
W. Bauer: http://www.lon-capa.org/∼mmp/applist/applets.htm
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10
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National Library of Virtual Manipulatives: http://nlvm.usu.edu/en/NAV/vlibrary.html
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Andrew Yue (compilation of applets site): http://www.ph.utexas.edu/∼phy-demo/resources/phys_applets.html
As you can see, most of these applet sites are professors or other scientists who have an interest in creating
applets. Therefore, check the information provided for scientic accuracy and whether the material is at the
appropriate level for your students.
3 In the Classroom
I have found four examples of applets that could be used when teaching on the topics of light and waves.
The rst two are more complex in their appearance and capabilities, and the second two are more simple.
Each has a place in the classroom, but it falls to the teacher to decide the level of sophistication necessary
to have the students understand the topic.
3.1 ExploreLearning.com Gizmos
Gizmos are interactive simulations that are fun, easy to use, and help students develop a deep understanding
of challenging concepts through inquiry and exploration. They are researched-based tools that are designed
to supplement the existing curriculum, by allowing the students to manipulate variables within a closed
environment (ExploreLearning.com). The gizmo I have found for light is about the eect a prism has on the
light, and the links are below. Another good feature about the Gizmos is a set of questions at the end of
each one, so the students may judge their understanding by how they are able to answer the questions.
13
http://www.explorelearning.com
/
http://www.explorelearning.com/index.cfm?method=cResource.dspDetail&ResourceID=608
7 http://galileoandeinstein.physics.virginia.edu/more_stu/Applets/
8 http://www.walter-fendt.de/ph14e/
9 http://www.edinformatics.com/il/il_physics.htm
10 http://www.lon-capa.org/∼mmp/applist/applets.htm
11 http://nlvm.usu.edu/en/NAV/vlibrary.html
12 http://www.ph.utexas.edu/∼phy-demo/resources/phys_applets.html
13 http://www.explorelearning.com/
14 http://www.explorelearning.com/index.cfm?method=cResource.dspDetail&ResourceID=608
http://cnx.org/content/m32280/1.2/
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Figure 2
3.2 University of Colorado at Boulder Physics Education Technology (PhET)
Again, these simulations are interactive tools that enable students to make connections between real life
phenomena and the underlying science which explains such phenomena. In order to help students visually
comprehend these concepts, PhET simulations animate what is invisible to the eye through the use of
graphics and intuitive controls such as click-and-drag manipulation, sliders and radio buttons. To further
encourage quantitative exploration, the simulations also oer measurement instruments including rulers,
stop-watches, voltmeters and thermometers.
As the user manipulates these interactive tools, responses
are immediately animated thus eectively illustrating cause-and-eects relationships as well as multiple
linked representations (motion of the objects, graphs, number readouts, etc. . .) (University of Colorado,
15
http://phet.colorado.edu/about/index.php
).
The applet I have chosen is about wave interference, and has three dierent ways to create interference:
water, sound, and light. Each presents its own unique style to understand wave interference, and through
the additional measuring instruments the students may further understand what is happening at a particular
point.
http://phet.colorado.edu/simulations/sims.php?sim=Wave_Interference
15 http://phet.colorado.edu/about/index.php
16 http://phet.colorado.edu/simulations/sims.php?sim=Wave_Interference
http://cnx.org/content/m32280/1.2/
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Figure 3
3.3 Paul Falstad's Applets
This site is short on explanation of applets, but long on examples written or compiled by Falstad. The main
site is http://www.falstad.com/mathphysics.html
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, and I have chosen one of the applets on dispersion. It
is relatively simple in its appearance and function, but is good at showing how two waves with dierent
frequencies and speeds combine as they form another wave.
http://www.falstad.com/dispersion/
17 http://www.falstad.com/mathphysics.html
18 http://www.falstad.com/dispersion/
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Figure 4
3.4 Physics Applets (Physlets)
Finally, Physlets Physics appletsare small, exible Java applets that can be used in a wide variety
of WWW applications.
Again, they are good for educational purposes, because they are simple, may be
modied to t almost any curricula and teaching style, and are exible. As seen in the screenshot, this applet
is also quite simple in setup and function. But, like the Falstad applet, it is good for changes to the waves
while still providing an understandable method of presentation. This applet is about the superposition of
waves, and in it students may change the amplitude and frequency of each wave to see the resultant wave.
http://qbx6.ltu.edu/s_schneider/physlets/main/waves_superposition.shtml
19 http://qbx6.ltu.edu/s_schneider/physlets/main/waves_superposition.shtml
http://cnx.org/content/m32280/1.2/
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Figure 5
4 Assessing . . . for the Classroom
4.1 Pro's
As seen in the examples section, applets may be simple or complex. This variation in function and form
is benecial by providing many dierent choices of presenting the information.
A teacher may choose to
demonstrate with one type of applet and have the students work on their own with another, each helping
the students to understand more completely. In addition, their easy-to-use software is compatible with many
dierent computers, and this makes less of a possibility to limit access for students. The applets may also be
used at any time in the inquiry cycle, anywhere from exploration to extend and elaborate. Their versatility
gives teachers much exibility when incorporating them into the curriculum. Finally, because they are not
actual experiments with physical ingredients, they are a much more cost-eective option for schools that do
not have the funds for complex physics experiments.
4.2 Con's
Because this is simply a simulation and not the real experiment, some level of interaction with the underlying
concepts may be lost. The applets must be checked for correct solutions and explanations of the concepts,
to ensure the phenomena are properly portrayed.
Each applet also requires its own computer, so lack of
computer space may be an issue.
5 Considerations for Teachers
1. Ensure the Java software is compatible with the computer(s) in the classroom.
2. Find a topic that would be enhanced by employing an applet. Search with a search engine or the above
starting places for an appropriate applet, and include in the topic.
3. Check the scientic accuracy of the applet, to ensure the content is aligned with current scientic
knowledge, state standards, and national standards.
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4. Think about where in the inquiry cycle or unit the applet would be most benecial and the level of
openness of the applet. Do you want the students to work on the applet completely by themselves, or
with some guiding questions? Are you simply using the applet as an in-class simulation or as outside
work? Answers to these type of questions will provide information on the most appropriate place to
include an applet and maximize the time spent with the applet.
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