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Author Topic: Propagation of Electromagnetic Wave  (Read 487089 times)
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Fu-Kwun Hwang
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on: January 29, 2004, 09:46:55 pm » posted from:,,Satellite Provider

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There are 18 translations,
Higher number at the end means more translation been done.
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You are welcomed to check out EM circular polarized wave or polarizer + EM circular/linear polarized wave

This java applet shows how the electric field, the magnetic field and the wave vector inter-relate as the electromagnetic wave propagates through space.



Red arrowBlue arrowGreen arrow
Electric field EMagnetic field BVelocity vector of wave V
fixedClick near tip of B then drag the mouse to change the velocity of the EM wavekeep E + V X B = 0


Press the start Button to start the animation.

The electromagnetic wave propagates in the opposite direction (from the origin).
Press the LEFT mouse button to pause the animation. Press it again to resume.
Press the RIGHT mouse button and drag the mouse to change the viewing angle.
Right click near the origin to move it.

T-field is the period (in seconds) [or 'fractions of a second' if referring to less than one second].
The speed of propagation remains constant but the period may vary ...(Thanks to Michael De Groot for his suggestion).
Press the Reset button to reset.

Thank Mark Servis for correction in the code (Oct. 8, 2001)
Your comments/suggestions are highly appreciated.


The following is a youtube movie about electromagnetic wave

http://www.youtube.com/watch?v=sS2ZyUvfUco


Registed user can get files related to this applet for offline access.
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There are 18 translations,
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or


* emspectrum.png (304.64 KB, 499x567 - viewed 27281 times.)

*** There are 1 more attached files. You need to login to acces it!
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Reply #1 on: January 30, 2004, 07:40:49 am » posted from:,,Satellite Provider

Subject: EM wave Applet
Date: Mon, 01 Sep 1997 17:34:13 -0700
From: "Sunil K. David" <davids@cookman.edu>
Organization: Bethune-Cookman College
To: hwang@phy03.phy.ntnu.edu.tw, rao@cookman.edu
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
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Reply #2 on: January 30, 2004, 11:38:05 am » posted from:,,Satellite Provider

Subject: E&M Waves
Date: Tue, 09 Mar 1999 00:34:41 -0800
From: Chun-Te Peter Wu <peterw@ucla.edu>
To: hwang@phy03.phy.ntnu.edu.tw
Hi Professor,
  I visited the your E&M website and I am very impressed with the animation
of the E&M waves. I especially liked the rotations of axis. Good Job
-Peter
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Reply #3 on: January 30, 2004, 11:42:02 am » posted from:,,Satellite Provider

Subject: Re: about your page in http://iswww4.moe.edu......emwave.html
Date: Tue, 23 Mar 1999 16:19:43 -800
From: jflores1@upb.edu
To: Fu-Kwun Hwang <hwang@phy03.phy.ntnu.edu.tw>
hi..

thanks 4 the help
my teacher liked the animation...!!!

and the rest of the class too..!!

once again thanks
http://www.upb.edu
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Reply #4 on: January 30, 2004, 12:53:45 pm » posted from:,,Satellite Provider

Subject: Electromagnetic wave propogation
Date: Thu, 21 Oct 1999 15:45:24 +0100
From: "Arif Zubairi" <zubairi@nortelnetworks.com>
To: "'hwang@phy03.phy.ntnu.edu.tw'" <hwang@phy03.phy.ntnu.edu.tw>
 
Hi

I was recently scouring the net looking for a suitable picture to
demonstrate the orthogonal mode of an electromagnetic wave in an optical
fibre for a presentation on polarisation dispersion (my artistic skills are
nil). I came across your moving Java applet description of an EM wave and
was suitably impressed as its exactly the type of picture I'm looking for. I
was wondering whether you might have still pictures of the sort that I might
be able to post in a Powerpoint presentation. If you do I would be much
obliged. Thanks

Regards
Arif Zubairi

Product Engineering
Nortel Networks
External: % 0181 945 3720
ESN: % 730 3720
E-mail: ) zubairi@nortelnetworks.com


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

thanks kindly. Much appreciated.
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Reply #5 on: January 30, 2004, 05:01:37 pm » posted from:Taipei,T'ai-pei,Taiwan

Date: Mon, 22 Jan 2001 22:03:52 -0500
From: Katrin Kneipp <KatrinKneipp@compuserve.com>
Subject: Your em wave animation
Sender: Katrin Kneipp <KatrinKneipp@compuserve.com>
To: "H.Wang" <hwang@phy03.phy.ntnu.edu.tw>

Dear collesgue,
I'm writing to kindlly ask you for setting a link to your em Wave animati=
on
from the home page of my Single Molecule Spectroscopy course, MIT course
6.975 Spring 2001.

http://ourworld.compuserve.com/Homepages/KatrinKneipp/6975.htm

Many thanks and best regards,
Katrin Kneipp

***********************************
Katrin Kneipp
Rockefeller Mauze Visiting Professor
Massachusetts Institute of Technology
Department of Physics
Department of Electrical Engineering and Computer Science
G. R. Harrison Spectroscopy Laboratory, Room 6-014
77 Massachusetts Avenue, Cambridge MA 02139-4307
Phone (617) 253 3378, Fax (617) 253 4513
e-mail:kneipp@usa.net
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dolanl
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Reply #6 on: May 05, 2004, 06:47:20 am »

Mr. Hwang:
In your animated propagation of EM waves, what is the green dot?


electrons have charge
photons have discrete enery which do not vary during propagation
light waves are compsed of photons(not electrons or positrons)
photons travel in straight lines

Are your graphics about electon emision?
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Fu-Kwun Hwang
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Reply #7 on: May 06, 2004, 07:30:23 am »

It could represent an oscillating charge (if this is the case: the simulation only show one of the possible EM-wave)
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Reply #8 on: May 06, 2004, 11:51:26 pm »

using a length of open-circuited transmission line, we can design a tuning stub to match a 75ohm line to (150-j75)ohm load.

What is the distance from the load to place the line, and legth of open circuited line. Do you know any method to solve this, other than smith's chart?

of what practical relevance is the design of matching stubs? what factors would dictate your selection of an open-circuited vs short-circuited?

Thanks, spectnas
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Reply #9 on: September 15, 2004, 04:13:37 am »

[b:63c7c331eb]Beautiful![/b:63c7c331eb]
 :shock: What a beautiful animation. To those who are curretly studying Electromagnetic Waves - like Í'm doing - this is a spetacular way of seeing how those fields propagates with a beam of light!

VF
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Fu-Kwun Hwang
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Reply #10 on: July 20, 2005, 10:44:15 am » posted from:Taipei,T'ai-pei,Taiwan

David Paraschuk :

> Hello,
>
> I was just running though some of your excellent java applets and I have a question concerning the propagation of EM waves. Every text resource or web resource depicts the E and B field components as reaching a maximum and minimum in phase. Yet the theory of Maxwell clearly indicates that the rate of field change in the mutual self-induction cycle is what is important, ( E∝ £GB/£Gt ). I think during the wave cycle when the E field is a maximum, the rate of change temporarily falls to zero and the the B field at that instant would be zero. The opposite would be true for the generation of the E field by a changing B field. Therefore a maximum E and B field can never be produced together in time and space.
>
> If this follows then the traditional drawings of the EM waves are incorrect and the wave peaks should be out of phase by 180 degrees!
>
> If you could briefly comment on this thinking I would be in your debt. Thank you.


It is the gradient of E in the space coordinate is proportion the rate of change in B field.
i.e. grad E = - dB/dt
It is different from E= -dB/dt (E and B should be out of phace)
So E and B do not necessary to be out of phase. They can be in phase or out of phase or other case (phase different not 90 degree).
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jashua
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Reply #11 on: January 14, 2006, 06:07:57 am »

shouldnt it be B X V = E instead of V X B = E ??
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Fu-Kwun Hwang
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Reply #12 on: January 14, 2006, 04:19:57 pm »

Sorry! It is corrected. It should be EXB=V or VXE =B or BXV=E ! :-)
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Helder de F. e Paula
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Reply #13 on: March 02, 2006, 05:03:09 am »

I want to get file related to EM Waves for offline use in my classroom.
Thank you.
Helder de F. e Paula
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Fu-Kwun Hwang
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Reply #14 on: March 02, 2006, 08:52:26 am »

Login to the forum and press "GET APPLET FILES" button near the end of the first message.
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Reply #15 on: August 26, 2006, 01:46:15 pm »

great job thanks for making physics so understandable to students.it really helps if we can show them what really happens then talking about what happens. congratulations. great combination of physics and programming.
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Reply #16 on: May 07, 2007, 01:42:14 am »

Hello!

Excellent animation! I'm doing a PowerPoint presentation about this subject. Is it possible to put this animation in my PoerPoint presentation, to be shown in a computer WITHOUT internet? If so, how can I do it?

Thanks.
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Reply #17 on: May 07, 2007, 11:38:00 pm »

As far as I know, java applets can not be embed into powerpoint.
However, you can download out applet and add a link in powerpoint to open the web page which contains java applets.
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Reply #18 on: July 05, 2007, 12:18:29 am »

hihi... can i have the source code? i was download the file, it is appear in .class file. is it possible view in source code from the .class file?
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Fu-Kwun Hwang
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Reply #19 on: July 10, 2007, 04:58:16 am »

You should have received source code now.
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Reply #20 on: February 06, 2008, 06:04:11 pm »

Hello Mr Huang and the rest of your team.
Congratulations for the great job you make.
I'm Kontellis George a teacher of Physics at 3rd Lyceum of Mytilini Greece.
I must thank you for the exciting Applets you have. Many topics of my teachings are much easier to teach with them.
I have two questions about EM waves.
1.  When EM waves transport inside an object is E/B equal with 300000000m/s or smaller?
2.  Near the antenna the two fields seem to have a phase difference of 90 but at a long distance their phase difference become zero. Why is that?
Thank you
George Kontellis
kontellis@sch.gr
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Fu-Kwun Hwang
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Reply #21 on: February 06, 2008, 11:33:53 pm »

1. E/B is the speed of the EM wave and the speed of EM wave is near c=3*108m/s in vacuum.
 But the speed is reduced to c/n when in an object, where n is the refraction index for that EM wave.
2. Could you explain why there is a 90 degree difference in phase for E/M wave  near the antenna?
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Reply #22 on: August 10, 2008, 07:57:31 pm »

i can`t use it offline
i`ve done the download of newest java
but it can`t work well...
no picture showned
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Fu-Kwun Hwang
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Reply #23 on: August 10, 2008, 09:18:55 pm »

What did you do with the downloaded file?
Did you unzip the file and open emWave.html with your browser?
I just tried it and it works fine with my browser.
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Reply #24 on: August 11, 2008, 01:28:09 pm » posted from:Taipei,T'ai-pei,Taiwan

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

I just created an EJS version for the same simulation.


The speed of the electromagnetic wave depend on the Electric field E and magnetic field B.
 v=E/B
For the same material, the ratio should be fixed.
If only one of them is changed, it mean wave traveling in different material (index of refraction is shown in the simulation).


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
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Reply #25 on: March 21, 2009, 01:33:49 pm »

when photons have no charge then how time varying electric and magnetic fields generate?
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Fu-Kwun Hwang
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Reply #26 on: March 21, 2009, 04:54:42 pm » posted from:Taipei,T\'ai-pei,Taiwan

Photon and EM wave are two different models (particle vs wave) to describe light.
You can check out modern physics textbook for related information.

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maxrk
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Reply #27 on: April 13, 2009, 10:55:10 pm »

Hi! Hwang
I very like your programing. I want to see source code java. I'm making project about electromagnetics.
please send me source code java  topic Electromagnetics
Thanks
Contact me : trcaoky@yahoo.com Smiley
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Fu-Kwun Hwang
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Reply #28 on: April 13, 2009, 11:32:30 pm » posted from:Taipei,T\'ai-pei,Taiwan

You should be able to find the source code (attached file at the top message) now.
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borlam
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Reply #29 on: April 22, 2009, 12:28:05 am » posted from:Troy,New York,United States

Hello,

If the default (reset) value represents the speed of light in a vacuum, then does this applet let you increase the speed of light?  Also, is it physically possible to have B greater than E?  It seems to me that would only happen if light were slowed to less than 1 m/s.  I read that physicists have slowed it to as little as 17 m/s. Would something bizarre happen to the nature of light if B were greater than E? Or would that not matter from a physics perspective.

I am grateful for your help in my understanding. Thank you.

 

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