There are more than one applet which is related to Suposition of Two Waves.
e.g. [url=http://www.phy.ntnu.edu.tw/ntnujava/index.php?topic=829.msg3142#msg3142]Suposition of Two Waves (with different phases)[/url], [url=http://www.phy.ntnu.edu.tw/ntnujava/index.php?topic=752.0]Superposition of two waves[/url] or [url=http://www.phy.ntnu.edu.tw/ntnujava/index.php?topic=19.0]Superposition Principle of Wave[/url]
Please give me the URL of the applet you are interested in.