This applet shown the diffraction/interference for multiplt slits.
Drag the [b]N[/b] slider bar to change the number of slits from 1-20. (1 for single slit)
Other slider bars at the bottom allow you to change the [b]Slit width[/b], [b]Slit separation[/b] and [b]Wavelength[/b] of the light source.
Slider bar on the top change the spatial resolution in the horizontal direction.
Slider bar at the right change the ntensity of the light source.
uncheck the checkbox to remove intensity plot (only display spectrum on the screen).

Virtual Physics laboratory Original URL

Fu-Kwun Hwang, Dept. Of Physics, National Taiwan Normal University.