DescriptionWave opposite-group-phase-velocity.gif	English: Animated Plot of a wave with phase and group velocities in opposite directions. ${\displaystyle y(x,t)=({\frac {5}{8))-{\frac {3}{8))\cdot \cos(2\pi (x-t)))\cdot \cos(2\pi (10x+4t))}$
Date	April 2011
Source	Own work;   This diagram was created with Mathematica.
Author	Geek3

 

This diagram was created with Mathematica.

Table[Plot[
  (5/8 - 3/8 * Cos[2 Pi (x - t)]) * Cos[2 Pi (10*x + 4*t)],
  {x, 0, 1}, PlotRange -> {-1, 1}, PlotStyle -> Thick, 
  PerformanceGoal -> "Quality" , ImageSize -> 250],
  {t, 0, 1 - 1/50, 1/50}]

File -> Save Selection As... -> wave_opposite-group-phase-velocity.gif

Bash commands for postprocessing (bash, ImageMagick, gifsicle):

$ convert wave_opposite-group-phase-velocity.gif -crop 268x192 +repage wave.png
$ for i in wave-*.png; do convert $i -crop 250x154+9+0 +repage $i; done
$ convert wave-?.png wave-??.png  wave_opposite-group-phase-velocity.gif
$ rm wave-*.png
$ gifsicle -b --delay 8 --comment "http://commons.wikimedia.org/wiki/File:wave_opposite-group-phase-velocity.gif" wave_opposite-group-phase-velocity.gif

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