/*  ================================================  Two-Slit Diffraction  ------------------------------------------------  Created by Søren Peo Pedersen - see my user page  at http://da.wikipedia.org/wiki/Bruger:Peo  ================================================  */    #declare WavefrontColor=<.2,.4,1>; // Wavefronts (default: blue)  #declare BarrierColor=<1,.8,.2>; // Barrier (default: Yellow)    union { // The barrier with two slits in it:  box {<-.1,.6,-.01>,<.1,5,.01>} // Part above the slits  box {<-.1,-.4,-.01>,<.1,+.4,.01>} // Part between the slits  box {<-.1,-5,-.01>,<.1,-.6,.01>} // Part below the slits  pigment {color rgb BarrierColor} finish {ambient 1}  }    #local Cnt=1; // Loop that puts some wavefront lines  #while (Cnt<5) // to the left of the barrier  cylinder {<(.5-Cnt)*0.37,-5,0>,<(.5-Cnt)*0.37,5,0>,.02  pigment {color rgb WavefrontColor} finish {ambient 1}}  #local Cnt=Cnt+1;  #end    // Arrows to indicate the directions of diffraction orders:  #macro OrderArrow(Start,End,Direction) // Macro to render one arrow  union {  triangle {<End,0,.01>,<End-1,-.3,.01>,<End-1,.3,.01>} // Forms an arrow  triangle {<End-1,-.1,.01>,<End-1,.1,.01>,<Start,.1,.01>} // stretching from  triangle {<End-1,-.1,.01>,<Start,.1,.01>,<Start,-.1,.01>} // Start to End a-  pigment {color rgb .6} // long the +X ax-  finish {ambient 1} // is, then turns  rotate <0,0,Direction> // it to Direction  }  #end  // Use the above macro to indicate 0th thru 2nd order diffraction:  #object {OrderArrow(1.3,3.3,47.73141557)} // 2nd order upwards  #object {OrderArrow(1,5.7,21.71561728)} // 1st order upwards  #object {OrderArrow(.5,5.4,0)} // 0th order horizontal  #object {OrderArrow(1,5.7,-21.71561728)} // 1st order downwards  #object {OrderArrow(1.3,3.3,-47.73141557)} // 2nd order downwards    // "m=(number)" legends at each diffraction order  #macro Mlig(Number) // Macro to render "m=" in bold italic, followed  union { // by the given Number in bold non-italic  text {ttf "timesbi.ttf" "m=",.01,0}  text {ttf "timesbd.ttf" str(Number,0,0),.01,0 translate <1.4,0,0>}  pigment {color rgb 1}  finish {ambient 1}  scale .6  translate <0,0,-.2>   }   #end  // Use the above macro to label each order of diffraction:  #object {Mlig(2) translate <.3,1.95,0>} // 2nd opder upwards  #object {Mlig(1) translate <3.1,1.8,0>} // 1st order upwards  #object {Mlig(0) translate <4,-.65,0>} // 0th order   #object {Mlig(1) translate <3.1,-2.1,0>} // 1st order downwards  #object {Mlig(2) translate <.3,-2.3,0>} // 2nd order downwards    // Angle-measuring "arcs" to indicate angles of diffraction:  #macro Angle(Degrees,Index,Radius)  union {  difference { // The arc part:  cylinder {<0,0,-.1>,<0,0,-.11>,Radius} // A cylinder, whose cur-  plane {<0,Degrees,0>,0} // ved surface defines the  plane {<0,-Degrees,0>,0 rotate <0,0,Degrees>} // arc, then parts of it  pigment { // are cut away using pla-  cylindrical // ne. Then it gets a cy-  color_map { // lindrical pigment thats  [0 color rgbt <1,1,1,0.5>] // transparent at the cen-  [0.2 color rgbt <1,1,1,0.75>] // ter so you only see it  [1 color rgbt <1,1,1,1.0>] // out near the curved  } // part.  rotate <90,0,0>  scale Radius  }  finish {ambient 1}  }  union { // "Nametag"; Greek "theta" with the given Index number:  text {ttf "symbol.ttf","q",0.1,0 pigment {color rgb 1} finish {ambient 1} scale .6 translate <-.2,-.2,0>}  text {ttf "timesbd.ttf",str(Index,0,0),0.1,0 pigment {color rgb 1} finish {ambient 1} scale .4 translate <.1,-.3,0>}  translate <(Radius+.3)*cos(radians(Degrees/2)),(Radius+.3)*sin(radians(Degrees/2)),-.2>  }  }  #end  // Use the above macro to indicate the angles of diffraction:  #object {Angle( 21.71561728,1,3)} // Show 1st order diffraction angle upwards  #object {Angle(-47.73141557,2,1.6)} // Show 2nd order diffraction angle downwards    #local Hole=-.5; // Loop run twice; once for  #while (Hole<1) // each slit in the barrier.  box {<-.6,Hole-.02,-.2>,<-.2,Hole+.02,-.1> // Little lines and  pigment {color rgb 1} finish {ambient 1} // triangular arrow-  } // heads showing the  triangle { // distance between  <-.5,Hole*.98,-.2>,<-.4,Hole*.5,-.2>,<-.6,Hole*.5,-.2> // the two slits in  pigment {color rgb 1} finish {ambient 1} // the barrier.  }    #local Cnt=1; // Loop run "several" (20) times to render concentric  #while (Cnt<20) // wavefronts emanating from each slit in the barrier:  difference {  torus {(Cnt-.5)*0.37,.02} // Torus to form the arc, minus a plane to  plane {<1,0,0>,.1} // cut away part of arc left of the barrier  pigment {color rgb WavefrontColor} finish {ambient 1}  rotate <90,0,0> translate <0,Hole,0>  }  #local Cnt=Cnt+1;  #end  #local Hole=Hole+1;  #end    union { // Various letters and arrowheads:  text {ttf "timesbi.ttf","d",0.1,0 // The "d" representing the distance  scale .6 translate <-.66,-.2,-.2>} // between the slits in the barrier  text {ttf "symbol.ttf","l",0.1,0 // Greek letter "lambda" representing  scale .6 translate <-.89,1.5,-.2>} // the wavelength  triangle {<-0.525,1.7,0>,<-0.325,1.6,0>,<-0.325,1.8,0>} // Arrowheads left and  triangle {<-0.955,1.7,0>,<-1.155,1.6,0>,<-1.155,1.8,0>} // right of "lambda"  pigment {color rgb 1} finish {ambient 1}  }    camera { // Viewpoint:  orthographic // No perspective  location <2.1,0,-5> // Looking from this position  look_at <2.1,0,0> // Looking towards this position  }