Comments/Suggestions From the Net (Thank
Your Suggestions/Comments are highly appreciated! Send
Subject: Buoyance force
Date: Sat, 16 Aug 1997 07:09:52 -0500
From: "K. M. Isaac" <firstname.lastname@example.org>
Organization: MM Enterprise
Your buyancy force animation is very good. I plan to use it in my fluid
K. M. Isaac University of Missouri-Rolla
Date: Wed, 20 Aug 1997 16:29:26 -0500
From: "efra璯 barbosa" <email@example.com>
Dear Prof. Hwuang:
I am also a physicist. I live in Bogota, Colombia.
I enjoy your simulations very much. It was a great work done by you.
Subject: WOW! Great sight
Date: Fri, 29 Aug 1997 16:48:04 -0600
From: Gary S Smith <firstname.lastname@example.org>
John P. Cise..Fac. Austin Com. College
Subject: EM wave Applet
Date: Mon, 01 Sep 1997 17:34:13 -0700
From: "Sunil K. David" <email@example.com>
Organization: Bethune-Cookman College
To: firstname.lastname@example.org, email@example.com
Hi: You have made my job quite simple in showing the prop. of EM wave
for my class.
Congratulations. Great applet. Goodluck, Bye,
Sunil K. David, M.Sc., M.Sc. Ph.D.
Assistant Professor of Physics
Subject: Your Physics Web site
Date: Wed, 03 Sep 1997 16:20:01 -0500
From: Narsing Rao <firstname.lastname@example.org>
Organization: Bethune-Cookman college
Hello Dr. Wang:
I just browsed your physics web site. I am really impressed
by what I saw.
I am sure my students will find it very useful and exciting.
I am not a programmer either, and just now I am trying to learn about
HTML and JAVA etc.
So long. I 'll be watching more of your pages.
Date: Sat, 06 Sep 1997 14:18:50 +0800
From: Cho-Teng Liu <email@example.com>
Dear Prof. Huang:
Your web pages are very exciting and it deserves an award in education
A minor suggestion:
While watching some of the experiment, e.g. the RC充/放電 電路,
the browsers will be more comfortable if they can view both the figure
and the text on the screen.
Therefore, I would like to suggest that
1) add a scroll bar for the text, or
2) place the title and figure on the left frame, and the text on the
Congratulation to your accomplichment.
Subject: java and sound
Date: Fri, 12 Sep 1997 14:19:41 +0800
From: "Harlan W. Lefevre" <firstname.lastname@example.org>
Dear Dr. Hwang,
I have used several of your applets in my physics courses here.
And I asked our people to mirror your site here for fast access.
The applets are really useful. Thank you.
I usually roll an NCD Xterminal into my classroom and use a remote
Sun as server.
Unfortunately java only writes audio to /dev/audio and Xwindows won't
deliver the audio to the Xterm.
So the beauty of your Fourier Synthesis program is largely lost when
one can't do the sound.
Do you have a solution to this problem?
Subject: pulley applet
Date: Fri, 26 Sep 1997 09:21:00 -0400
From: "Robert B. Muir" <email@example.com>
Organization: Physics & Astronomy, UNC Greensboro
To: firstname.lastname@example.org, email@example.com
You have done a very good job developing these wonderful applets.
I have not run all of them yet, but look forward to doing so.
I just tried the Pulley applet and had a problem.
It seemed to download, but nothing ever appeared in the display area.
The text below the display area looked ok.
I am running Netscape Communicator 4.01 on a 166 MHz Pentium with 30
Mb of Ram.
All the other applets I have tried worked ok.
Thank you for making this material available to us all.
Sincerely yours, Bob Muir
Physics & Astronomy
U North Carolina at Greensboro
Greensboro, NC USA
Date: Tue, 7 Oct 1997 00:29:04 +2.00
From: "H L Botha" <firstname.lastname@example.org>
Organization: Iscor Profile Products
Hallo Mr Hwang
I enjoyed your web site , good work !!
Herman Botha (South Africa)
Date: Fri, 17 Oct 1997 13:19:20 +0000
From: David Johnson <email@example.com>
Organization: Douglas High School Science Department
I've used your vector addition and vernier caliper applets in my physics
and physical sciences classes.
I'm just sending this note to thank you and ask you to keep up the
Subject: your educational Java applet(s)
Date: Mon, 20 Oct 97 17:53:34 -0700
From: Martin Koning Bastiaan <firstname.lastname@example.org>
To: "Fu-Kwun Hwang" <email@example.com>
Dear Java Educational Applet Author,
Thanks for creating a great educational applet and making it available
on the WWW.
Your Java applet is pointed to by the Educational Object Economy (EOE),
located at http://trp.research.apple.com/.
Apple Computer, Inc.零 EOE Team is preparing to distribute an EOE framework
(which we雹e calling the GOE--Generic Object Economy)
and its URL directory to groups who wish to set up their own EOE.
Please reply to this message if you would NOT like a pointer to your
applet(s) (shown below) included in this release.
If you have written other educational applets in Java and would like
to see them included in our EOE database,
please contact us. You can even enter your applets into our database
If you find any out-of-date or incorrect information, either listed
below or on our site
(which contains more thorough descriptions of the Java applets than
is listed here),
please let us know so that we may update our records.
For more information about the GOE: http://trp.research.apple.com/info/goe.html
Martin Koning Bastiaan,
Educational Object Economy
Date: Sun, 26 Oct 1997 08:49:37 -0800
From: Ursula Sexton <firstname.lastname@example.org>
Hello, Mr. Hwang, I am an elementary science teacher,
as well as a leader in science education reform in the state of California.
I train teachers and while searching for some physics principles, I
found the Web site with your applets.
I was interested in seeing your rainbow demonstration. It is so wonderful!
This site is just full of great demonstrations for clarifying principles
that teachers just can't seem to grasp,
unless a visualization tool is provided. This is just great!
I thought I'd mention that there is a small mispelling at the bottom
of your rainbow page.
Your last bullet reads: "Did yo noticed that rainbow consists
of partially polarized light.
It should say - for grammar and spelling to be correct:
Did you notice that the rainbow consists of partially polarized light?
Best of luck in your journey to share with others the wonders of science.
Thanks for the gift of your knowledge and the wonderful medium to share
Subject: standing wave
Date: Wed, 03 Dec 1997 10:26:03 +0000
From: Keli Sato <email@example.com>
Organization: Addison Wesley
Hello, I visited your Superposition Principle of Waves (http://www.phy.ntnu.edu.tw/java/waveSuperposition/waveSuperposition.html).
The applet is great, but I think you ment to say Standing wave, not
Subject: Superposition of waves
Date: Mon, 15 Dec 1997 20:37:48 +0100
From: Peter Ryder <firstname.lastname@example.org>
Organization: University of Bremen
Your Java applet for superimposing wave is very nice,
but the "medium" has the interesting property that the group
velocity and the phase velocity have opposite signs!
Well, that makes an intersting problem for the students to discuss.
Subject: RC circuit applet
Date: Sun, 11 Jan 1998 06:41:16 +0000 (!!!First Boot!!!)
From: "Samara, Thomas Nick" <email@example.com>
Thanks alot for your program.
I couldn't quite find in the book a description of what the current
was doing while the capacitor was charging.
Please make more programs like it.
Subject: Doppler effect and shock wave
Date: Sat, 17 Jan 1998 20:49:55 +0700
From: Amrat Chawla <firstname.lastname@example.org>
Even though I am in trading business, in my personal time I am very
much interested in Physics
and I bought some 1st year university text book to study Physics as
But frankly, your web site give me a very clear lesson just in few
that I discovered your site I understand a lot !!.
For example I try to understand the sonic-boom but even I read many
time I still cant get it,
but with just few minute of virtual experiment with 'Doppler effect
and shock wave' it became clear to me !!
Really thankyou very much for your site.
I regard you as my teacher.
With respect and best rgds.
Subject: This site is so cool!!!
Date: Fri, 23 Jan 1998 16:10:28 -0600
From: Michele Gale-Sinex <email@example.com>
Thanks for sharing it.
center for integrated ag systems
Subject: Pulley Experiment
Date: Sun, 25 Jan 1998 13:14:53 -0600
From: "Radim Kolarsky" <firstname.lastname@example.org>
Dear Dr. Hwang:
My son and I have enjoyed visiting your site today and yesterday, looking
at your experiments.
In an effort to assembe information for my son's school science project,
we attempted to see the "Pulley" page but, unfortunately,
the link is broken.
I have marked your site among my bookmarks and will definitely come
Radim A. Kolarsky
Subject: Pulley and more...
Date: Mon, 26 Jan 1998 20:57:05 -0600
From: "Radim Kolarsky" <email@example.com>
Dear Dr. Hwang:
Thanks for fixing the link and making the page available again.
I have been looking for a while for this type of an on-line physics
textbook. Your page is just great.
Please keep up this good work. I work as a geologist/applied geophysicist
at Shell in New Orleans.
Originally, however I was born in Czechoslovakia and came to the U.S
as a political refugee in 1987.
I will never forget my high school physics professor (whose picture
my wife and I keep on our web page)
I had there as a student. He did quite a bit for me.
Thanks again. SHould you efer come to New Orleans (a convention perhaps)
please do not hesitate to let us know.
Subject: Request for the secret!
Date: Tue, 27 Jan 1998 23:57:11 +0800
From: "Stephen, W. T. Kwan" <firstname.lastname@example.org>
I am Stephen W. T. Kwan, a secondary teacher in Hong Kong.
Your java applets are too amazing that I cannot help writing to you
Would you please mind telling me how you develop these kinds of programs
the time needed to do so?
Actually, I want to develop similiar programs myself in Hong Kong.
You can contact me through my e-mail address email@example.com.
Thank you for your attention.
Stephen, W. T. Kwan 27/01/98
Subject: Orbit applet
Date: Fri, 30 Jan 1998 08:44:52 +0530
From: "Surendranath Reddy.B." <firstname.lastname@example.org>
To: "Hwang" <email@example.com>
I just saw your orbit applet. It was just the thing that I thought
I would suggest to you.
Please consider the following suggestions.
Would it possible to show the initial position of the projectile,
its velocity and the angle the velocity makes with the line joining
it and the center of the earth
and then give the option to launch.
The distance from the center of the earth could be made large ( twice,
thrice.. the radius of the earth)
It would be better if the user gives these inputs by mouse clicks or
by entering the values.
( It may be also a good idea to relate these values with (gr)^0.5,
the value required for a circular orbit. One could bring out the concept
of escape velocity also.
Date: Sat, 31 Jan 1998 11:41:23 -0500
From: "Pierce C. Barnard" <firstname.lastname@example.org>
Hi, I was examining your satellite & projectile motion applet and
I found it to be very useful.
A suggestion, you may want to allow a user to set all paramters and
provide a button on the applet to start the applet.
This way the user will not have to keep on readjusting the applet while
the projectile is in motion.
Date: Sun, 01 Feb 1998 17:08:13 -0600
From: John Eagle <email@example.com>
I think this page is great.
I stumbled into it one night while trying to find some insight on a
physics assignment that I had.
I've used it ever since to check my work.
Something that might be helpful to a great number of people
would be a java applet with thick lenses and or two lense systems.
Just a thought.
Thank you for taking the time to publish such a page John Eagle
*** Please check out Thick Lenses
Date: Wed, 11 Feb 1998 21:51:07 +0800
From: tiffany cheng <firstname.lastname@example.org>
hi, This is my first time to be here, your homepage. What can I say???
It's unbelievable! It's fantastic! It's perfect! Here, I'm writing
this letter is to encourage you to keep doing this job.
It really gives people answers. GO! GO! GO!
Subject: Your Java Frictionnal Force applet.
Date: Mon, 9 Feb 1998 11:45:31 +0100
From: "leflocht" <email@example.com>
Thanks a lot for your on-line physics lesson.
As a french teacher i would like to ask you the permission to use your
applet on a new html sheet
using french as basic language. Of course i would only translate your
words( the best i can)
and leave each reference (native URL, mailto.. and comments in original
The reason is that i just gave my students, (aged 17) a exam using
the study of this system.
So i would like them to use your applet to get more of this study case
by using new parameters
such as Mu and various masses.
This page, if possible, will be added to the site i create for my sudents
(it's the very beginning),
you could surf at: http://www.chez.com/bup/index.htm and find it using
french "Fichiers de TP" in the 1S section.
---- You ask for suggestions ? Of course i've got some.
*first: The masses you use : Are F1 = 10 grams or F1 = 10*g where 10
is kg and g is 9.81 mS-2 ?
(and so on for others )? case 10 grams: we use to calculate Force intensity
in Newton (France) case 10 kg:
the mass seems very heavy !
*second: Some lines of your HTML page are not readable for french users
because of the asian keyboard
translation,( i think.) Just above the definition table of forces,
there is a line i'dont know what it is ?
(caracters like @#& and others not in use in our alphabet but for
bad words ...)
The definition for f12 is quite the same it appears like: f12j[number
zero]m1 g[symbol for english pound] g
I think we must read: f12 not so different of m1. Mu.g. ad so on for
each reading of friction force. -----
I can make, if you look for it, other text translations, so your work
to make your work used by french people.
Thierry Le Floch Thanks to disregard my english mistakes.
Thierry Le Floch
Email: firstname.lastname@example.org site
Date: Wed, 11 Feb 1998 11:43:06 -0400
From: Hugo Beltrami <email@example.com>
To: firstname.lastname@example.org CC: email@example.com
Hello, I was looking at your site and I was wondering whether it would
to mirror it here at this university. Would you please let me know
if this is possible.
Then I would contact our system manager Thank you for your attention
-- Hugo Beltrami
Department of Geology
Fax : 902-867-2457
St. Francis Xavier
P.O. Box 5000, Antigonish
Nova Scotia, Canada,B2G 2W5
Date: Thu, 12 Feb 1998 16:57:50 -0600
From: Taha Mzoughi <mzoughi@Ra.MsState.Edu>
Organization: Mississippi State University
Dear Professor Fu-Kwun Hwang:
This is the first of two emails I will be sending you.
I have been familiar with your work for about a year now. To say the
list, it is impressive.
I am an assistant professor of physics at MS State University and I
try to use the Web for instruction.
The URL for my class is: http://webphysics.ph.msstate.edu/2213.html
I am still working on the content and would like to eventually include
some of your Java applets.
Obviously maintaining links to your Web site and proper credit.
I have noticed that you have your applets mirrored throughout the word
(which is nice)
and I am wondering if it acceptable for you to add another mirror in
I am also interested in having a copy of the applets to run of laptop
that is not connected to the Web.
Actually, I am giving a talk about resources on the Web for teaching
physics to high school teachers
on the 20 th of February, and I hope to be able to include some of
I will write a page with links to the applet in your site that I will
use in the presentation then place it on our server.
I appreciate your help. You are doing some neat stuff there.
Department of Physics and Astronomy
PO Box 5167
Mississippi State University
Mississippi State, Mississippi 39762-5167
Phone: (601)325 2923
Fax: (601)325 8898
Subject: Java and Physics
Date: Sun, 15 Feb 1998 09:15:22 +0100
I am a professor of physics at the Royal Institute of Technologu in
We do teach Java for programming in Science and I came across your
Although we do teach Java for Ph.D. students I think there is something
that could be learnt
from your beautiful pages. Maybe we will also extend the course to
The problem is that we are in physics and Java should be taught by
the CS dept, but will they do it our way?
We may try to suggest a course and then some of your web pages could
be very useful to the students.
I would therefore like to ask you about your plans etc.
I would hate to have made refs to your pages and then they would disappear
one day, smile.
Also, you may have some new ones in mind?
I think something with the uncertainty principle would be very useful.
Have you ever considered this?
I am very open for any form of collaboration on this future teaching
You can find examples of the present course on the web.
We plan some lecture notes and I hope I can make ref/use some of your
Looking forward hearing from you
// Thomas Lindblad
Subject: Physics Java Applets
Date: Sun, 15 Feb 1998 15:37:15 +0800
From: Stephen Chin <firstname.lastname@example.org>
Dear Sir, I'm also a Physics teacher, O level, and I am interested
by the Java Applets you have created..... they are really good.....
I find them very useful for teaching and demonstrating certain concepts
I am wondering how do you write a Java Applet....
I have the Java Programmer Kit downloaded from Sun.... but don;t know
how to use it.....
Thanks in advance.
-- If we wait long enough we may reap the best harvest....
Subject: Publishing Your Applets
Date: Tue, 17 Feb 1998 18:38:33 -0600
From: Taha Mzoughi <email@example.com>
Dear Professor Fu-Kwun Hwang
My name is Taha Mzoughi and I am an assistant professor of Physics at
Mississippi State University. I am currently compiling a library of Web-based
simulations and animations for a CD-ROM to accompany the forthcoming third
edition of Jones and Childers' CONTEMPORARY COLLEGE PHYSICS book. The library
will supplement software developed for the book by McGraw-Hill publishing.
The intent is for me to write an HTML page including a link to the selected
web resource along with credit to the author and text relating the animation/simulation
to the book content. In some cases, we might need to include operation
instructions. To reduce problems due to web traffic and to changes in web
addresses we prefer to include a copy of the actual animation/simulation
on the CD.
As a bound-in supplement to the book, the CD is intended to provide
the student with increased resources and a pathway to the resources available
on the Web without augmenting the cost of the book. We are mainly interested
in material that students can access for free on the Web. Credit to authors,
links to their sites, and any other material that we (or you) feel is needed
will be provided. I particularly like some of the simulation/animations/applets
you have developed and think that they are excellent candidates for the
library. The applets I am seeking permission for are at the following URLs:
hrough this email, I am formally asking you for permission to include
your simulation/animations/applets in the Contemporary College Physics
CD. If you accept this offer, McGraw Hill Publishing will send you a printed
version of the agreement. Obviously, to include your software in the CD,
we need assurances that you have full rights on all of its content. If
you are not the appropriate person to contact for permission, please let
me know whom to contact. Agreeing to include your simulation/animations/applets
in the CD will give McGraw Hill Publishing a NONEXCLUSIVE right to distribute
the software free of charge with the book.
I believe your simulation/animations/applets to be an excellent educational
tool and I would like to help get more students to take full advantage
of it. I am looking forward to the possibility of working with you on this
Please note that the publishing schedule is tight and I need your reply
ASAP. You may contact me at firstname.lastname@example.org (phone 601-325-2923)
or contact McGraw Hill Publishing directly by sending email to David Dietz
at email@example.com. Please include your "snail mail"
address in your reply.
We request permission to use the material in Jones/Childers third edition
and subsequent editions of that book (this is standard for excerpted material),
but not in other books. The permission letters reads:
We request your permission to include the following material on the
bound-in CD-ROM in this and all subsequent editions of the book, including
versions made by nonprofit organizations for use of blind or physically
handicapped persons (and in all foreign language translations and other
derivative works), for distribution throughout the world.
[Taha Mzoughi] I hope that this is fine with you. Your Applets are great
and students and teachers will greatly benefit from having them readily
available. I have made a presentation Friday to about 60 teachers from
around here. I showed some of your applets and they loved them. Most of
the teachers still don't have internet access readily available. Remember
also that you are retaining the right to publishing the applets elsewhere.
Subject: java applets
Date: Sun, 01 Mar 1998 01:45:54 -0500
From: Clifford Sampson <firstname.lastname@example.org>
Dear Mr Hwang
I have found your java applets especially those on waves and optics
to be particularly facinating and informative.
So much so that I have begun to use them extensively for my grade 11
at Appleby College in Oakville, Ontario, Canada. ...
Date: Mon, 02 Mar 1998 13:32:38 +1100
From: masukor <email@example.com>
Hi, been to your physics lab. great stuff.
I teach physics at a junior college here in australia.
I certainly will make more visit to your site. bye.
Subject: Your Doppler effect applet
Date: Sun, 8 Mar 1998 22:39:05 -0600
From: "Michael Vershinin" <firstname.lastname@example.org>
Your applet is pretty neat, but since you asked for suggestions...
1) I would not allow the user to set a negative wavelength.
2) If negative source speed is chosen, your source runs off the edge
of the window.
3) Negative wave speed is a bit awkward, since your source is actually
Subject: Thank you for the applet!
Date: Tue, 10 Mar 1998 10:34:26 +0100
From: Uwe Gaertitz <email@example.com>
To: "'firstname.lastname@example.org'" <email@example.com>
your applet works fine, thanks a lot.
We want to use it offline, for non-commercial demonstration.
I've mentioned you and made references to your site at this local page,
1. One goal is to maximize/minimize :-)
the flow. But it's so easy, with setting velocity and acceleration
to max(min), isn't it?
2. It would be fine to see the flow rate in an extra text field,
cause this is the much interesting output (for me).
3. Perhaps, a "history" of the last flow rates (then you
can better see,
whether you have success in maximizing flow rate or not).
Could be a simple text table (over a time intervall), or a graph.
Subject: I saw a Polarized Rainbow!
Date: Sat, 14 Mar 1998 01:18:24 -0800
From: Neal Rasmussen <firstname.lastname@example.org>
I am, as far as I know, the first to see a "Polarized Rainbow"!
I think we should name this phenomona the "Rasmussen-Wang Rainbow".
I am a tornado chaser for 20 years. About 4 years ago I was driving
through a McDonald's drive thru.
As it was just after a pretty good storm, I had mys polarized yellow
tinted flip-up sunglasses on.
Low and behold I almost dropped my cigarette into my lap.
There off in the east was a double rainbow!
Not the kind I've seen dozens of times where the second one is reveresed
and much outside the primary,
but this was immediatly INSIDE the primary!
Gaping with my mouth open and people behind me honking,
I flipped my flip-ups up and the second inner one went away!
I must have sat there for 2 minutes flipping my sunglasses.
The colors were NOT reversed and it looked like one continuous double
with two complete sets of colors.
I ruled out that the flip-ups where giving double vision as I looked
at lights the next day,
streetlights headlights, etc. and no doubles!
Can this possibly be? Could a source of polarized light be at a different
perhaps the sun shining through a cirrus cloud or noctelucent (sp).
Neal Rasmussen email@example.com
Subject: Can I add a counter to the mirror site?
Date: Tue, 24 Mar 1998 19:02:33 +0800
From: "tanghb" <firstname.lastname@example.org>
Dear Mr. Hwang,
When I meet the physics teachers of the other schools in Singapore,
they give good comments about the mirror site of Virtual Physics Laboratory.
I think your Java Applets are popular in Singapore.
I am therefore interested to know how many people come to visit Virtual
and use your Java applets everyday.
Mr. Hwang, can I add a counter on the contents page?
If so, please let me know.
Tang Hung Bun
Singapore Chinese Girls' School
Date: Fri, 03 Apr 1998 16:16:37 -0600
From: Kelly <email@example.com>
Mr. Hwang, I want to say that your virtual lab was unbelievably helpful
I attend the university of wisconsin-madison and I was having problems
with optics concepts.
I went under the internet and searched under lens and mirrors and fell
upon your lab.
I am very grateful. I was a little upset last night when I wanted to
access the lens mirror applet,
because I couldn't find it.
I guess even the virtual labs have hours of availability.
I guess that's my only suggestion,
which isn't a very necessary one to attend to when most of us can access
it during the day.
Thanks again, Chris firstname.lastname@example.org
Subject: Refraction Applet
Date: Thu, 23 Apr 1998 10:14:02 -0400
From: Sandee Coats-Haan <LA_COATSHAA@PO.SWOCA.OHIO.GOV>
To: hwang <email@example.com>
Is there any way to change the velocity vector and/or the medium thickness
on your refraction applet if you don't have a two button mouse?
Sandee (Lakota East High School Physics)
P.S. -- you have an incredible site
Subject: Java 動畫
Date: Mon, 27 Apr 1998 18:44:50 -0700 (PDT)
From: Dan Murray <firstname.lastname@example.org>
也發現了國立 台灣師範大學的物理系的網頁﹐所以發現了你的許多 Java 動畫。
直到 現在﹐我沒有意識了物理教師創造了那麼許多 Java 動畫。
但是﹐你供 應更多消息是適當。我的電腦是 Windows 3.1 的 PC 。
即使我使用比 較新近的 Netscape （就是 3.05）還不可以看見 Java 動畫。
最低的 電腦需要是 Windows 95。或許你可以給人講解﹐所以阻止挫敗。
我們 有 Windows 3.1 的人應該知道﹐ 惟有看見 Java 動畫的方法大概是買
可惜﹐因為我是物理教授﹐無奈繼續使用我的舊電腦﹗ Dan Murray 謹上
Subject: (no subject)
Date: Wed, 29 Apr 1998 22:13:08 -0500
From: Dion Sanchez <email@example.com>
I want to thank you for this page, it has helped me visualize what
a text book could not.
I have been looking for something like this for a long time.
great stuff thanks. dion
Date: Sun, 03 May 1998 12:47:55 -0600
From: The Lahrs <JohnJan@lahr.org>
I love your thin lens page: http://www.phy.nau.edu/~layton/JavaApps/thinlens/lens_e.htm
What a great use of Java!
I use Netscape, by the way, and the applet worked just fine and was
I've been trying to figure out why a glass rod creates an inverted
(about one axis) virtual image.
Do you have an applet for a thick lens, or just a ray diagram that
would show this effect?
Is the thinlens.java code still available? The link was not working
when I tried.
It would be interesting to develop something like this for seismic
I'm a seismologist now, but my first love is physics,
which was my undergraduate major at Rensselaer Polytechnic Institute.
Thanks again for providing the world this great applet.
John C. Lahr
-- * John C. and Jan H. Lahr * *
JohnJan@lahr.org * *
914 10th Street * *
Golden, Colorado 80401 * *
(303) 215-9913 * *
http://www.lahr.org/john-jan * *
Date: Sun, 03 May 1998 15:39:11 -0600
From: The Lahrs <JohnJan@lahr.org>
I just figured out that the inverted image is not virtual but real,
so everything makes sense now.
Keep up the good work.
John C. Lahr
Subject: problems with cyclotron java applet
Date: Thu, 4 Jun 1998 19:37:38 +0200
From: "Pietro Diviacco" <firstname.lastname@example.org>
My name is Pietro Diviacco. I am an Italian surgeon and live and work
in Genova, Italy.
I tried to play Your applet "Cyclotron" but there was some
Some of the images (*.gif 7 and 14) were not available and the applet
was not working.
In any case Your applets are very good and interesting (the working
ones, of course).
Thank You in advance for fixing the problems.
E-mail address: email@example.com
Subject: Web Site
Date: Mon, 8 Jun 1998 18:11:12 EDT
Hi! I'm a physics teacher in Blantyre High School in Scotland
and I've just discovered your Physics demos site.
When I return to school tomorrow I'll be directing my class to your
site first thing.
Well done and thank you...
I'll be a regular visitor from now on.
Subject: Great jobs!
Date: Sun, 14 Jun 1998 17:37:43 +0800
From: "Robinson Wang" <firstname.lastname@example.org>
Dear Mr. Hwang,
Hello! I am a student of the National Tsing Hua University(NTHU).
Maybe you've heard that the Material Science Engineering which is my
I'd like to appreciate the great jobs you've done.
At first, I come to this website because of my final-term physical
However, when I view the first exam, I can't help finishing all items
in this site.
Well, that's all what I want to say about this special work.
Have you a happy time in teaching.
Your sincerely, Robinson Wang '98.6.14
Subject: Enjoyed your supersonic applet
Date: Mon, 29 Jun 1998 15:30:54 EDT
I enjoyed studying your applet.
I have taken the liberty of making some minor wording changes so that
your description will be more grammatically correct.
I wish I were multilingual as you are! ;-)
The location of supersonic airplane.
If an airplane is flying faster than the speed of sound, it will produce
a sonic boom or shock wave.
As shown in the right figure, consider an airplane which is flying
from A toward B.
A listener is located at C. The sound generated at A travels toward
C along the path AC.
The listener hears the sound as the airplane flys toward point B.
( AB > AC ) DC is the path of the sound generated at D to the listener.
The airplane speed is V and the sound speed is Vs.
If AC/Vs > AD/V + DC/Vs [Isn't it unlikely that the shorter path
will take a longer time?],
then the sound generated at point D will arrive earlier than sound
generated at point A! Funny!
You hear something which happened later and then hear something which
happened earlier !
What will you hear if a supersonic airplane flying over you?
Do you know where is the airplane when you hear it?
Can you point out the direction of the airplane just from hearing the
This java applet let you play with such situation.
Press Start to start the animation. A listener is represented by an
You can press the left mouse button and drag it within the screen to
change location of the listener.
The program draws sound wave paths to the listener.
The animation will be suspended when the sonic boom arrives at the
Click the right mouse button to continue. The color of the paths changes
The order in which the sound paths arrive at the listener are shown
You can change the ratio of airplane speed of airplane to sound speed
and see the difference.
Date: Sat, 04 Jul 1998 11:57:20 -0700
From: Daniel Murphy <email@example.com>
I'm a student at Olympic College in Bremerton, Washington currently
enrolled in a physics class.
We are studying vectors, freefall, velocity/acceleration and projectile
Your web page is great!
I think the answer to the question of case one about the green circle
is the arc of zero vertical velocity.
When the object reaches zero velocity, acceleration remains a constant
9.8 m/s(sq) downward.
ubject: Your applets
Date: Fri, 24 Jul 1998 13:13:16 -0400
From: firstname.lastname@example.org (Mike Diegel)
My friend and I had been discussing what a sonic boom is
and I was trying to describe how the sound waves come together to make
We came across your web page at
and used the applet. We thought it was a fantastic illustration of
what a sonic boom is,
and we just wanted to let you know that your work was appreciated.
Thanks for the help.
Subject: Conservation of Linear Momentum
Date: Tue, 28 Jul 1998 09:14:28 +0800
From: Lim Ai Phing <email@example.com>
I'm a physics teacher presently teaching my students dynamics.
Your collision java applet is really good, I'll ask my students to
take a look here!!
But can I suggest that the colour of the numbers be changed
because yellow doesn't show up much against a gray background?
Subject: Thanks for great BioSavart
Date: Mon, 24 Aug 1998 22:16:57 -0700
From: "Sunpainter" <firstname.lastname@example.org>
I was looking for something on the shape of circuit for very small
trying to predict some electromagnetic field changes in the circuit.
I will be using very, very small current.
Your simulation was incredibly, wonderfully helpful!
If I had to do all the math for each current change, it would have
taken me forever.
Now I have my figures. THANK YOU THANK YOU!
It is for a strange little generator I am building.
K. Hodge Southern California
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作者：國立台灣師範大學 物理系 黃福坤