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"There is nothing either good or bad, but thinking makes it so." ..."Shakespeare (154-1616, English dramatist and poet) "

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 Author Topic: refraction of wave from one media to another media  (Read 21015 times) 0 Members and 1 Guest are viewing this topic. Click to toggle author information(expand message area).
Fu-Kwun Hwang
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 « Embed this message on: February 02, 2008, 12:03:16 am »

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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.

You can find another similar applet at Reflection and Refraction
For light (electromagnetic wave):

 substances Air Water Plexglass Diamond indices of refraction 1.00029 1.333 1.51 2.417

For sound wave :

 material Air water vapor fresh water sea water Aluminum speed of sound (m/s) 331 401 1493 1513 5104

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tanghb
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 « Embed this message Reply #1 on: February 02, 2008, 11:28:05 am »

Thank you so much for creating this useful applet. Many physics students will benefit from it.
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tanghb
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 « Embed this message Reply #2 on: February 02, 2008, 05:06:09 pm »

Dear Fu-Kwun,

When I set cta= 45.0 and index of refraction = 1.45 and let the simulation run for a while, some additional lines start to appear on the medium in the right hand side (please see screeshot below). The simulation will come to a stop soon after this. Is this an error? Thanks.

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Fu-Kwun Hwang
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 « Embed this message Reply #3 on: February 02, 2008, 10:49:04 pm »

I can not reproduce what you have found. But I found another bug in the code.
Could you try it again and let me know what need to be improved to fit your need!
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tanghb
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 « Embed this message Reply #4 on: February 04, 2008, 09:36:19 am » posted from:Singapore,,Singapore

I have tried it a few times and everything works fine now. Thank you very much.

By the way, it is possible to adjust cta to 0o so that students can see that the wave direction does not change although the wave speed changes?
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Fu-Kwun Hwang
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 « Embed this message Reply #5 on: February 04, 2008, 10:58:41 pm »

I just modified the code. You should be able to adjust cta to zero now.

Let me know if you need more function for this java applet (simulation).
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"There is nothing either good or bad, but thinking makes it so." ..."Shakespeare (154-1616, English dramatist and poet) "