Ejs Open Source Single Slit Diffraction Model

[lookang]

Ejs Open Source Single Slit Diffraction Model by Fu-Kwun Hwang remixed by lookang

reference:
Superposition of several waves http://www.phy.ntnu.edu.tw/ntnujava/index.php?topic=2082.0 by Fu-Kwun Hwang

Embed a running copy of this simulation
<applet code='users.sgeducation.lookang.wave_singleslit2wee03_pkg.wave_singleslit2wee03Applet.class' archive='http://www.phy.ntnu.edu.tw/ntnujava/ejsuser/14019/ejs_wave_singleslit2wee03.jar' name='wave_singleslit2wee038663' id='wave_singleslit2wee038663' width='450' height='550' mayscript=true><param name='draggable' value='true'></applet>
Embed a running copy link(show simulation in a popuped window)
<a href='http://www.phy.ntnu.edu.tw/ntnujava/msg.php?smfejs=8663' target='smfejs'>Run simulation</a>

Full screen applet or Problem viewing java?Add http://www.phy.ntnu.edu.tw/ to exception site list
Press the Alt key and the left mouse button to drag the applet off the browser and onto the desktop. This work is licensed under a Creative Commons Attribution 2.5 Taiwan License

• Please feel free to post your ideas about how to use the simulation for better teaching and learning.
• Post questions to be asked to help students to think, to explore.
• Upload worksheets as attached files to share with more users.

Let's work together. We can help more users understand physics conceptually and enjoy the fun of learning physics!

other interesting single slit ejs applets
Single Slit diffraction http://www.phy.ntnu.edu.tw/ntnujava/index.php?topic=128.0 by Fu-Kwun Hwang
Like: intensity


Youtube
http://youtu.be/sjmBcm84iA4

http://www.youtube.com/watch?v=sjmBcm84iA4

[lookang]

changes:

redesign the way the scalar-Field is calculated using a dynamic way that is always correct and to scale instead of the older way of 2 separate scalar-field.

Code:

for(int j=0;j  for(int k=0;k  zsum[j][k]=0;
  }
 }

 
for(int i=0;i yc=yi+i*dy; // lay the source in y
 ycc[i] = yi+i*dy; // by lookang for drawing source
 
 for(int j=0;j //  if (x  x=xmin+j*d;
 //  }
 //  else if (x>x1){
//  x=x1+j*d;
  // r=x-x1; // r is distance from array point x to slit position x1
//  x2=(x-xc)*(x-xc);
//  }
  for(int k=0;k  y=ymin+k*d;
 
  if (x  r=x-x1; // r is distance from array point x to slit position x1
  zsum[j][k]=Math.sin(kw*r-omega*t)*n; // need n to compensate for the magnitude
  }
  else if (x>=x1){
  r=Math.sqrt((x-xc)*(x-xc)+(y-yc)*(y-yc));
  zsum[j][k]+=Math.sin(kw*r-omega*t);
  }
 
  }
 }
}

add ns to n and draw the sources with checkbox
add wavelength and drawing checkbox etc
add width and checkbox
add type and colormode for different visualization especially cool is the 3D view that required a square array [200][200]
add step of step by step animation

enjoy!

[lookang]

http://en.wikipedia.org/wiki/Huygens%E2%80%93Fresnel_principle

http://upload.wikimedia.org/wikipedia/commons/thumb/6/60/Refraction_on_an_aperture_-_Huygens-Fresnel_principle.svg/2000px-Refraction_on_an_aperture_-_Huygens-Fresnel_principle.svg.png

Huygens[1] proposed that every point to which a luminous disturbance reaches becomes a source of a spherical wave, and the sum of these secondary waves determines the form of the wave at any subsequent time.

Same Huygens-Fresnel principle Refraction on an aperture (slit) but notice the secondary source space equally apart and start from center ending 1/2 space from the edge of slit which is more logical than end at the edge of the slit.

Same Animation Huygens-Fresnel principle Refraction on an aperture (slit)

Huygens assumed that the secondary waves traveled only in the "forward" direction and it is not explained in the theory why this is the case. He was able to provide a qualitative explanation of linear and spherical wave propagation, and to derive the laws of reflection and refraction using this principle.



http://electron9.phys.utk.edu/phys136d/modules/m9/diff.htm

Diffraction is a phenomenon whereby waves appear to bend around obstacles, or appear to spread out after passing through a small orifice. The occurrence of
diffraction allows us, for example, to hear sounds from sources that are
 hidden from us by some obstacle or other.

http://www.physchem.co.za/OB12-wav/diffraction.htm the map reminds me that to easily remember this diffraction occurs when w slit width is comparable to  λ wavelength.

Diffraction is a wave phenomenon and is also observed with water waves in a ripple tank. A wave spreads out (noticeable diffraction)  when the size of the slit is comparable to or smaller than the wavelength. When wave passes through a small opening, comparable in size to the wavelength, in an obstacle (in this case yellow rectangles) , the wavefront on the other side of the opening resembles the wavefront shown below.

http://electron9.phys.utk.edu/phys136d/modules/m9/diff.htm

 In the Ejs simulation case,

when slit width is comparable in size to the wavelength

same animation when slit width is comparable in size to the wavelength

The wave spreads around the edges of the obstacle (yellow in this case).  This is the phenomenon of diffraction.  Therefore, diffraction is "spreading out " wave phenomenon.



http://electron9.phys.utk.edu/phys136d/modules/m9/diff.htm has some photo of the real ripple tank.

http://electron9.phys.utk.edu/phys136d/modules/m9/diff.htm when slit width is comparable in size to the wavelength

http://electron9.phys.utk.edu/phys136d/modules/m9/diff.htm when slit width >> in size than the wavelength

in Ejs,I managed to capture a similar computational model.

when slit width is comparable in size to the wavelength assuming 6 secondary sources, diffraction is noticeable

slit width >> in size ( w = 6*λ ) than the wavelength assuming 10 secondary sources. A wave goes largely straight when the size  of the slit is much larger than the wavelength

I love Phet research and simulation

this is a great simulation called Wave Interference, under the water tab, the simulation breaks the 2D with a side view.

Click to Run

I managed to figure out a cool way to generate a 3D visualization is Ejs.

when slit width is comparable in size to the wavelength assuming 6 secondary sources, diffraction is noticeable

 

slit width >> in size ( w = 6*λ ) than the wavelength assuming 10 secondary sources. A wave goes largely straight when the size  of the slit is much larger than the wavelength

my favorable visualization is

Spectrum visualization of when slit width is comparable in size to the wavelength assuming 10 secondary sources, diffraction is noticeable

Spectrum visualization of slit width >> in size ( w = 5*λ ) than the wavelength assuming 10 secondary sources. A wave goes largely straight when the size  of the slit is much larger than the wavelength

other interesting slit simulation are:

http://www.falstad.com/ripple/





Contribution to benefit the world at wikimedia

Date	Name	Thumbnail	Size	User	Description
13:26, 14 October 2011	5wavelength=slitwidthsprectrum.gif (file)		580 KB	Lookang
13:26, 14 October 2011	Wavelength=slitwidthspectrum.gif (file)		580 KB	Lookang
13:26, 14 October 2011	Wavelength=slitwidthblue3D.gif (file)		483 KB	Lookang
13:26, 14 October 2011	Wavelength=slitwidthblue.gif (file)		768 KB	Lookang
13:26, 14 October 2011	6wavelength=slitwidthblue3D.gif (file)		464 KB	Lookang
13:26, 14 October 2011	6wavelength=slitwidthblue.gif (file)		527 KB	Lookang
13:26, 14 October 2011	Wavelength=slitwidth.gif (file)		825 KB	Lookang
13:26, 14 October 2011	Diffractiongreen.gif (file)		838 KB	Lookang
13:26, 14 October 2011	Diffractionblacknwhitewavelength4timesslitwidth.gif (file)		741 KB	Lookang
13:26, 14 October 2011	Huygens Fresnel Principle.gif (file)		796 KB	Lookang