Standing wave via reflection

The black dots represent a string. [b]Click "Reset",[/b] then click the "Play" button to send a traveling wave down the string![br][br]Upon reaching the end of the string (at right), the red wave will produce a reflected blue wave. The string will respond to the superposition (sum) of the two traveling waves.[br]The green slider controls whether the end of the string is free or fixed.
[i]This is my attempt at a GeoGebra version of the original Java applet by Walter Fendt, now superseded by his HTML5 interactive animation at [url=https://www.walter-fendt.de/html5/phen/standingwavereflection_en.htm]https://www.walter-fendt.de/html5/phen/standingwavereflection_en.htm[/url][/i]

Information: Standing wave via reflection