Hi, First of, you have some great applet here. I used the double slit applet here the other day in my class, and it was great. However I would like to have a similar applet for a grating (you don't by any change have one ready, do you? :D). So is there a change I can see your source code for the double slit applet: http://www.phy.ntnu.edu.tw/ntnujava/viewtopic.php?t=36 Best Regards Frank