Subject: SV: Doppler applet wish (& propagation) Date: Fri, 28 May 1999 09:28:04 +0100 From: Jeff Forssell <> To: "''" <> CC: Claes Ahlin <> 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 <> To: "'Fu-Kwun Hwang'" <> 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 <> To: "'Hwang'" <> CC: Claes Ahlin <> 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.