Subject: Doppler effect and shock wave
Date: Sat, 17 Jan 1998 20:49:55 +0700
From: Amrat Chawla <amratc@mozart.inet.co.th>
To: hwang@phy.ntnu.edu.tw
Dear Sir,
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 hobby.
But frankly, your web site give me a very clear lesson just in few days
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.
Amrat Chawla

ubject: Your applets
Date: Fri, 24 Jul 1998 13:13:16 -0400
From: diegel@med.unc.edu (Mike Diegel)
To: hwang@phy03.phy.ntnu.edu.tw
Fu-Kwun,
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 it happen.
We came across your web page at
http://didaktik.physik.uni-wuerzburg.de/~pkrahmer/ntnujava/Doppler/Doppler.html
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.
Mike
Mike Diegel
diegel@med.unc.edu 966-9100

Subject: SV: Doppler applet wish (& propagation)
Date: Fri, 28 May 1999 09:28:04 +0100
From: Jeff Forssell <JF@ssvh.se>
To: "'hwang@phy03.phy.ntnu.edu.tw'" <hwang@phy03.phy.ntnu.edu.tw>
CC: Claes Ahlin <AI@ssvh.se>
Thank you! That was fast!

The doppler applet is more flexibla now. I would though prefer if one
could lefdt press and drag between 2 freely chosable points and get
delta x, delta y; rather than only distance from source.
 Another detail is that the y coordinate is negative upwards which is
not the most common matematically, though those distances aren't so
interesting.

You might be interested to know that the doppler applet was referred to
in one of the questions in the latest National Exam in Physics. But we
aren't allowed to disclose the contents. (So erase this letter :-) )

I assume the index.html page was in Chinese (It sure wasn't English!)
 

The propagation applet is perfect. Whoops I just noticed that for large
angles of incidence, the incident beam became solid red!


--------------------------------------------------------------------------------

Subject: SV: SV: Doppler applet wish (&propagation)
Date: Mon, 31 May 1999 05:43:14 +0100
From: Jeff Forssell <JF@ssvh.se>
To: "'Fu-Kwun Hwang'" <hwang@phy03.phy.ntnu.edu.tw>
I notice that if I enter a user ratio in propagation, the top and bottom
field maintain the colors it had before, no matter whether the ratio is
more or less that 1. Maybe it would be good to have the optically more
dense media become gray.

  I see that you have put in the angles also. I thought of suggesting
that but I forgot to write it.

A new idea I got was is: could the intensity of the beam colors show how
much of the radiation is reflected and transmitted. No big need, but it
would be nice, even if just approximate. But that would be complicated
because polarization comes in also. That would be a challenge! Maybe
better with a separate applet. But you have made some amazingly compact
versatile applets before. (Like the lens /mirror one!)

I think there maybe is a serious flaw in the doppler applet: example
with the default settings the wavelength is supposed to be 20. If I
measure on the right it is 20 and left it is 60 if i change the speed
to 4 the measured distance between wavecrests becomes: 42 38 which
seems to indicte that the wavelength is actually 40. I' m in a bit of a
hurry until wednesday so I may have made a mistake.



--------------------------------------------------------------------------------

Subject: more ideas for doppler and propagation applets
Date: Wed, 2 Jun 1999 09:29:17 +0100
From: Jeff Forssell <JF@ssvh.se>
To: "'Hwang'" <hwang@phy03.phy.ntnu.edu.tw>
CC: Claes Ahlin <AI@ssvh.se>
I just got an idea för the doppler applet that I hope you will like:
[ ] listener in top part

if someone checks in the box, the user can place a "listner" anywhere in
the window.
Whenever a wavefront passes him the computer makes a sound (a beep or
tick or something).
For example: I place my listner in front of the advancing source:
beep beep beep beep beep (then it passes) beep beep beep beep
If I place my listener off to the side I would get a less pronounced
effect
(what should happen when a supersonic "bang" arrives should of course be
some loud noise).

Another wish for the propagation applet:
increase the n1/n2 options with "diamond to air". I think people
tend to be fascinated by diamonds and they do have a spectacularly
high n value. (I saw that in another persons refraction applet, which
also included the possibility to show wavelength changes (also different
colors for the different wavelengths) but I prefer yours otherwise)



--------------------------------------------------------------------------------

Thank you for your answer. I have a lots of tests to grade now at the
end of the term. Perhaps it is the same for you.

Subject: SV: SV: SV: Doppler applet wish (&propagation)
Date:  Mon, 7 Jun 1999 07:06:02 +0100
From:  Jeff Forssell
To:  "'hwang@phy03.phy.ntnu.edu.tw'"
CC:  Claes Ahlin
I am in a bit of a hurry with other things also, but I have looked at the
applets and they look good!

You made a very nice interface for seeing the reflection of different
polarized waves. Both numerical and visual without cluttering up the
previous features!
Jeff Forssell
personal homepage:  http://www.torget.se/users/i/iluhya/index.htm
my village technology homepage:  http://home.bip.net/jeff.forssell
Swedish National Institute for Distance Education (SSVH)
Box 3024  SE-871 03 Härnösand /Sweden
tel +46(0)611-55 79 48  fax +46(0)611-55 79 80
schools homepage  www_ssvh_se
residence +46(0)611-22144

>----------
>Från:  Fu-Kwun Hwang[SMTP:hwang@phy03.phy.ntnu.edu.tw]
>Skickat:  den 7 juni 1999 03:20
>Till:  Jeff Forssell
>Angående:  Re: SV: SV: Doppler applet wish (& propagation)
>
><><><><>propagation.class>>
>Jeff Forssell wrote:
>
>> I notice that if I enter a user ratio in propagation, the top and bottom
>> field maintain the colors it had before, no matter whether the ratio is
>> more or less that 1. Maybe it would be good to have the optically more
>> dense media become gray.
>>
>>  I see that you have put in the angles also. I thought of suggesting
>> that but I forgot to write it.
>>
>> A new idea I got was is: could the intensity of the beam colors show how
>> much of the radiation is reflected and transmitted.  No big need, but it
>> would be nice, even if just approximate. But that would be complicated
>> because polarization comes in also. That would be a challenge! Maybe
>> better with a separate applet. But you have made some amazingly compact
>> versatile applets before. (Like the lens /mirror one!)
>>
>
>Try the attached java applet and let me know if this is what you want.
>Pick p-wave or s-wave from the top left selection.
>
>
>>
>> I think there maybe is a serious flaw in the doppler applet: example
>> with the default settings the wavelength is supposed to be 20. If I
>> measure on the right it is 20 and left it is 60  if i change the speed
>> to 4 the measured distance between wavecrests becomes: 42 38  which
>> seems to indicte that the wavelength is actually 40.  I' m in a bit of a
>> hurry until wednesday so I may have made a mistake.
>
>In my previous java applet, the distance between wave front is not necessary
>related to the wavelength. Those are wave front generate at fix time interval
> not necessary equal to period of the wave).
>In this attached java applet it is modified so that the wave front is
>generated
>with the same period of the wave. Try it and let me know what you think.
>
>I will try to add sound effect at the next release.
>But you will have to wait a few days,
>I will have to do other stuff first.
>
>

When I wrote a moment ago about a BASIC program I had and decimal
acceptance, I got to thinking maybe your applet could be expanded (or a
new one with similar components so It could replace this program for
practicing reading analog scale instruments:

It is written i Qbasic. (There is also less common scale where range 12
V is to be interpretted from a printed scale with 6 V as full scale-
I've seen similar things in reality but that aren't very common so I
might take that away.)
That I don't have more scale divisions depends on 2 things:
1) I want students to practice estimating tenths of scale divisions
2) lack of time (laziness?)

I m sending  this qbasic file  (and another on Vernier scale)
As a friend of "old" computers I have versions for CGA and Hercules
screens too

Jeff Forssell



--------------------------------------------------------------------------------

Yes we really do use commas for decimals!  We even use (sometimes)
periods as thousand separators.
We do end our sentences with . though.

I was amazed to hear from you so quickly. I found myself wondering what
is the time In Taiwan? We are at 17 degrees longitude and taiwan at 120
so that should mean that when you sent your letter it must have been
around 6 pm your time. (I don't know if you use Daylight saving time
there).

Both the class files were smaller than the old ones! How is that
possible? Did you do some code cleaning when you added features?

Were you able to open the Qbasic files?

Thanks! The mails were from people on my Loan Calculators allow list...

AWSOME!!!!! :lol: :lol: :lol: :lol: :lol:

You will get files related to java applet when you click "download applet files for offline use".  You will find more simulations in Chines at http://www.phy.ntnu.edu.tw/demolab/phpBB/

There are hundreds of physics related java applets in this forum. You are welcomed to check it out.
Suggestions for the applets are highly appreciated!

Because some one posted a question in Chinese, so I just posted previous message to tell him/her that we have more simulations in Chinese  on our Chinese physics forum.
When I created java applets for physics topics, I will create a Chinese version first. Then, I will  add a English version when I have free time. So there are more applets in our Chinese forum , and there are many  other multi-media for physics teaching,too. But I do not have time to translate all of then into English.  Because I do all of this with my free time(after work).  What I can promise is: If you need any simulation for physics teaching/learning and you can not find a similar one from the net, you can post it at Request for physics Simulations .
 I will try to create one for you as soon as possible.

I think it is due to your browser did not support java. You can download Java Runtime Environment (JRE) from sun's web site and install it on your computer.