Subject: SV: SV: SV: Doppler applet wish (&propagation)
Date:  Mon, 7 Jun 1999 07:06:02 +0100
From:  Jeff Forssell
To:    "''"
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:
my village technology homepage:
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[]
>Skickat:        den 7 juni 1999 03:20
>Till:  Jeff Forssell
>Angående:      Re: SV: SV: Doppler applet wish (& propagation)
>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
>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

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?