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Author Topic: Reflection and Refraction  (Read 497633 times)
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Fu-Kwun Hwang
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1 Reflection and Refraction
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on: January 29, 2004, 05:55:50 pm » posted from:,,Satellite Provider

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There are 27 translations,
Higher number at the end means more translation been done.
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The Transmission of Wave through Dense media -- Reflection and Refraction



The Huygens–Fresnel principle:It recognizes that each point of an advancing wave front is in fact the center of a fresh disturbance and the source of a new train of waves; and that the advancing wave as a whole may be regarded as the sum of all the secondary waves arising from points in the medium already traversed.



How to play:


  1. The whole area has been divided into two region (Top/Buttom).

  1. Click within the black semi-circular near the top , then drag the mouse (Left-Right) to change the angle of incidence.

  2. You can enter the ratio of index of refraction for those two media (n2/n1).

  3. Click Faster/ Slower to change the wave speed.

  4. Suspend/Resume the animation.


    1. The animation is suspended when you press down the left mouse button, it is resumed when you released the mouse button.

    2. If you press the right mouse button, the animation is also suspended. But you will have to press the right mouse button again to resume the animation.

    3. What if I press the right mouse button first then press the left mouse button ? Try it!


* For sound wave originates in and impings on water:

If the incident angle is larger than critical angle (about 13 degree),

the sound wave will be total reflected. No sound will be transmitted.



When a beam of light impings at some angle on the smooth flat surface of an optically dense medium, the wave "sees" a vast array of very closely spaced atoms that will somehow scatter it.
(At the wavelengths of light -- d=500nm -- the Earch's atmosphere at STP has about 106 molecules in such a d3-cube).
As the wavefront descends, it excites one scatterer after another, each of which reradiates a stream of photons that can be thought of as a hemispherical wavelet in the incident medium.
Because the wavelength is so much greater than the separation between the molecules, the wavelets advance together and add constructively in only one directions, and there is one well-defined reflected beam.
The wavelets bend as they cross the boundary, because of the speed change.
For similar reason, they form one well-defined refracted beam.





Ratio of index of refraction n2/n1 = v1/v2, where v1, v2 are speed of wave in media 1 and 2.
For light (electromagnetic wave):


substancesAirWaterPlexglassDiamond
indices of refraction1.000291.3331.512.417

For sound wave :


materialAirwater vaporfresh watersea waterAluminum
speed of sound (m/s)331401149315135104



http://www.youtube.com/watch?v=xwzw5GhpC_0


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There are 27 translations,
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* wavepropagatione1.png (28.18 KB, 668x445 - viewed 29675 times.)

*** There are 1 more attached files. You need to login to acces it!
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Reply #1 on: January 30, 2004, 11:22:10 am » posted from:,,Satellite Provider

Subject: fed.cuhk.edu.hk/sci_lab/ntnujava/propagation/propagation.html
Date: Tue, 10 Nov 1998 23:00:38 -0500
From: "Mark C. Barnett" <mcbarnet@indiana.edu>
To: <hwang@phy03.phy.ntnu.edu.tw>
fantastic web page. i'm doing a report on wave division multiplexing and
found your web site very useful and easy to use. thanks for the help.

mark
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Reply #2 on: March 30, 2004, 03:11:40 am » posted from:Oshkosh,Wisconsin,United States

I'm lazy and want to have this post on the top... so I am posting. Aren't I smrt?
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Pilimala
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Reply #3 on: April 01, 2004, 04:30:45 pm »

Why the speed of sound is faster in Aluminium? Is it related to the density of a material? :shock:
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Christina Pilimala
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Reply #4 on: November 15, 2004, 07:43:27 pm »

This is really fantastic, I have a suggestion.I think if the path of the wave (directions) are not indicated by the colours,it would have been better. But still you know better.
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Reply #5 on: August 28, 2005, 05:47:54 pm » posted from:Paris,Ile-de-France,France

This is a very nice Applet. Thank you.
Can I use it for my students? Where was it taken from?
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Fu-Kwun Hwang
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Reply #6 on: August 29, 2005, 10:01:21 am » posted from:Taipei,T'ai-pei,Taiwan

You will find a button labeled "GET APPLETS FILES" near the end of the first message (if you are a registered user and login to the system).
Just click that button and files related to this applet will be packed and send to your email account.

Fu-Kwun :-)
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Lucciano
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Reply #7 on: September 29, 2005, 11:03:52 pm »

Please help us to receive thouse applets class files , just because theres no GET APPLETS FILES button available, tks .This is an lovely work , excelent job .Congratulations for this. Cheesy
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radio anda data transmitions are the leading edge of my stuff interest
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Reply #8 on: November 03, 2005, 07:35:16 am » posted from:Malappuram,Kerala,India

I want the source code of this applet
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Fu-Kwun Hwang
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Reply #9 on: November 03, 2005, 03:40:59 pm » posted from:Taipei,T'ai-pei,Taiwan

You need to login to find the "GET APPLET FILE" button!
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santa_thanapol
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Reply #10 on: November 11, 2005, 12:37:54 pm »

You need to login to find the "GET APPLET FILE" button!
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Petr
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Reply #11 on: April 08, 2006, 04:54:25 pm » posted from:Chodov,Karlovarsky kraj,Czech Republic

I like it very much.

Is there a chance to change an area between this two xxxions. Thanks to black points and mouse for example - I like circle etc.

If there is a chance to get the source file, not only the class, then i will try it by myself.

Thanks for answer on my email. Smiley Smiley Smiley Smiley
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green8003
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Reply #12 on: April 30, 2006, 11:06:53 pm »

hi
im glad to watch these simulations.But i have a question.why i dont watch all of simulations.only afew simulations i can see.i dont suppose that from me.because some simulations when i click them i see but others i didnt.

if u express me this i will be happy.

thanks...
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Fu-Kwun Hwang
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Reply #13 on: May 01, 2006, 11:35:22 am »

There are two categories: Simulationsunder Physics simulation (current one) are created by JDK1.0.2 almost 10 years ago. Most browser should be able to support it.

For those simulations under "Easy Java simuations (EJS)" are created with EJS and need latest java installed. You need JDK1.5 and above. You need to download and install latest JRE (Java Run time Environment)
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Pinhas
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Reply #14 on: June 09, 2006, 12:26:21 am »

How do I download this applet?
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Fu-Kwun Hwang
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Reply #15 on: June 09, 2006, 10:30:19 am » posted from:Taipei,T'ai-pei,Taiwan

You will find button labeled as "GET APPLET FILES" at the end of the first message if you are login to the forum.
Click that button and files will be deliveried to your email account.
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sonia_martins
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Reply #16 on: November 06, 2006, 07:42:15 pm »

When I downloaded the file, the language was not english. could you please send to my mail acount the english file please.
thanks
(soniag_martins@hotmail.com)

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Fu-Kwun Hwang
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Reply #17 on: January 27, 2007, 11:30:52 pm »

index.html is Chinse version but you should also find english verson file: propagtion.html


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Fu-Kwun Hwang
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Reply #18 on: February 02, 2008, 09:04:40 am »

Registed user can get files related to this applet for offline access.
Problem viewing java?Add http://www.phy.ntnu.edu.tw/ to exception site list
If java program did not show up, please download and install latest Java RUN TIME

Here is another version created with EJS


It recognizes that each point of an advancing wave front is in fact the center of a fresh disturbance and the source of a new train of waves; and that the advancing wave as a whole may be regarded as the sum of all the secondary waves arising from points in the medium already traversed.

The following images are linked from WiKi page: http://en.wikipedia.org/wiki/Huygens%E2%80%93Fresnel_principle


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Problem viewing java?Add http://www.phy.ntnu.edu.tw/ to exception site list
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ametz
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Reply #19 on: June 29, 2008, 03:59:39 am »

This is a nice applet indeed.
Yet I think I've found a small bug.
When the index of refraction is decreased below 0.22 (e.g. for sound from air to glass it is 0.06) the critical angle remains at 12.9 degrees.
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Fu-Kwun Hwang
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Reply #20 on: June 29, 2008, 08:56:51 am »

You can enter ratio for index of refractions if you select "user defined ratio =>".
And you need to hit ENTER after you enter new value for the new value to have effect.
Please try it again and hit ENTER.
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ametz
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Reply #21 on: July 05, 2008, 04:11:08 am »

Thanks for your reply. I indeed forgot to hit ENTER. The program is working fine!
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jahokka
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Reply #22 on: January 15, 2009, 02:43:42 am » posted from:Pori,Western Finland,Finland

Hi!
I am impressed. So impressed, that I hope I could translate some of your sites. I have downloaded some works to my self and translated then (with many words = teathers habits). There is one translation in finnish I have uploaded to your site, but there was some difficulties with the ISO 2202, I supose. Finnish code-system use UTF-8 with some Latin-1 extenssions. We uses two letters, witch are imported, but is not included in UTF-8 Latin-1 basic collection (A - Z).

Is there anything to be done?
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Reply #23 on: January 15, 2009, 10:31:59 am » posted from:Taipei,T'ai-pei,Taiwan

Thank you very much for making translation in Finnish.
I found out one of the teacher download nearly four hundreds simulations from this wet site and translation it into Slovokia's language two years ago when I went to a conference. (He handed me the CD with all the translation). I was so impressed. And I knew that he has to download all the files one by one and create the translation.
So I created a simple user interface  to help user translate web page.
You can click "translate this message(and the string in the simulation) into local language" button.
Because there are so many character code used by different country.
So I adope "utf-8" system. Please change the coding in your browser to utf-8 when viewing the web page.
(normally, the browser will switch to utf-8 when loading web page from this web site, unless you change the default coding to always stick to some particular coding).

If you can not find the coding for your language from the menu, please give me the full name of the coding. I will try to find information about your language and implement into the system. And I will need your help to test it when I modify the code. Do you know the official name for your utf-8 coding system? (UTF-8 Latin-1???)  Chinese characters are also two letter code.
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jahokka
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Reply #24 on: January 18, 2009, 01:22:38 am » posted from:Pori,Western Finland,Finland

According to wikipedia in english, the codepage following standard ISO-8859-1 include all the letters I need to write finnish. Standard 8859-1 is synonymous with Latin-1. Browsers from Nothern Europe, Germany, ect. uses it.
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Fu-Kwun Hwang
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Reply #25 on: January 18, 2009, 08:14:20 pm »

Because user live in different country use different language coding system.
If the HTML page was written with ISO-8859-1 , then user has to select ISO-8859-1 in order to view it correctly.
And our server has to know your coding when you submit your data.
If different user use different language coding, it will be difficult to handle it.

UTF-8 can prevent this kind of difficulty. Please change your coding to UTF-8 before your do the translation. The default seeting for the browser was automatically switch to the language coding according to server information. Our server already sent out information tell browser to switch to UTF-8 when doing the translation. May be your browser has been set to fixed language coding. Please change it to automatic mode or change it to UTF-8 when you want to do the translation.
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Reply #26 on: January 20, 2009, 03:37:41 am » posted from:Pori,Western Finland,Finland

Thank you for your time. I'm in hurry now, but I will return on the subject on the end of the week. Then I will try these tricks you told me. I hope they works and I can start this hobby. ;-)
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qzoners
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Reply #27 on: September 01, 2009, 09:01:24 am » posted from:Bandung,Jawa Barat,Indonesia

Fu-Kwun, you are rock!

You make phisic learning is so easy to understand. Thanks for this great job
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daryy
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Reply #28 on: September 06, 2009, 12:14:41 pm » posted from:Beijing,Beijing,China

I make sure  if the path of the wave (directions) are not indicated by the colours,it would have been better. Is it ok?any good idea?
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Fu-Kwun Hwang
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Reply #29 on: September 06, 2009, 10:54:25 pm » posted from:Taipei,T\'ai-pei,Taiwan

You are wlecomed to download the source code : propagation.java
And change the color to wherever you want.
Please post it here when you  find out a better solution.
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Teaching without words. ...Lao Tzu (570-490 BC)
 
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